Lecture 36 - Poster Presentation Practices
Please read and prepare for Wednesday Dec 7 ahead of time. Bring your printed posters (black and white are fine for this practice).
Please read and prepare for Wednesday Dec 7 ahead of time. Bring your printed posters (black and white are fine for this practice).
Grades have been posted.
This blog posting is due on Dec 7 before class.
There is no need to post in the blog. You will do this activity in class (Nov 28). Read the instructions provided on Monday November 21.
Prior to Monday class
1. Identify your assignments by looking at this file.
You may also wish to download a copy of the example poster that Edgar and Chad will critique.Chem4101-Poster-critiquing.pdf
3. Re-read the "Guidelines to prepare your analytical problem" posted in the blog at the beginning of the semester. Pay particular attention to items 5, 6, and 7.Defining and solving analytical chemistry problems-2011.pdf
3. Get familiar with the poster that you will critique on Monday. Based on your table assignment, choose one of the options below.
Post your answers by November 21, 2011 (before class).
Posting due on Wed November 16, 2011 before class
Everybody will need to prepare a one minute presentation. You will need to fill up the table found in the lecture notes and create a new blog comment.
If you wish to use a power point presentation, let me know ahead of time. Also bring your laptop and your VGA adaptor.
This blog posting is due on November 11, before class.
Please note that the due date is before the beginning of the exam next Friday (Hint!)
Date: October 26, 2011
Time: 8:15 to 8:45
Location: 191C Kolthoff Hall
Facility Director: Dr. Joe Dalluge
Similar to seminars, bonus points will be given to those posting in the blog after attendance to this facility visit.
Answer only one of the questions below.
1. What ionization sources are available?
2. What mass analyzers exist in the facility?
3. What instruments are interfaced with HPLC or other separation techniques?
4. What are projects currently using the facilities?
5. Are there any other ionization sources or mass analyzers in the facility that we did not cover in class?
6. What instrument(s) at the facility can be used to investigate your analytical problem?
7. If none of the instruments at the facility is suitable to investigate your analytical problem, what instrument would you say is needed to investigate your analytical problem.
8. What questions do you have that were not answered?
Postings are due on October 28, before class
Due October 26, 2011 before class.
Due Wednesday 19 before class.
Due October 17, 2011
Please refer to the presentations given in class on October 5, 2011. Posting is due Friday October 7, 2011.
Please let me know by Monday (Sep 3) evening if you plan to use a power point slide.
Dowload this file and use it to keep notes on other presentations.
Lecture13-111005-Analytical problem presentations.pdf
Recently more and more products such as Diana and Lemon Herbal Whitening Cream have shown up in the markets with mercury levels well over the permitted federal limits, of less then one parts per million, of mercury. Some of these products have shown levels of 33,000 parts per million of mercury. With these products finding their way to shelves of stores through informal trade it is difficult to keep track of them. Therefore these products continue to circulate. Mercury is an extremely toxic element and exists in nature in many different types of forms and oxidation levels, with the most common being Mercury (II). Mercury in bleaching and cosmetic creams were introduced the early 1900 when it was discovered that Mercury was extremely effective in lightening dark spots and stubborn pigmentation but it also had a high remission rate. Nevertheless bleaching creams with high levels of Mercury was aggressively marketed to black people. In 1976 Mercury was banned in the EU when it was discovered that it had damaging side effects. The US banned the use of Mercury in cosmetic creams much later in 1990. The reason Mercury was banned was it proved to be very toxic and can absorb through the skin and cause neurological affects and can even poison and shut down certain organisms like the kidneys.
My hypothesis is the mercury in these products cause a lot of health issues especially pertaining to communities such as the Somali community in which these products keep showing up in.
1. Skin-Lightening Products Found to Contain Mercury: Minnesota Department of Health. http://www.health.state.mn.us/topics/skin/ (accessed September 19, 2011)
2. Lide, D. R., ed (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. pp. 4.125-4.126. ISBN 0-8493-0486-5
UV-Vis absorption spectrometry
As I mentioned before Mercury exist in many different forms like the organic mercury found in fish, methylmercury. However the Mercury found in most of these cosmetic creams is inorganic Mercury (II) usually mercuric chloride (HgCl2) or mercuric amidochloride (HgNH2Cl). Inorganic Mercury is soluble in alcohols so an ideal solvent would be ethanol because various types of inorganic Mercury (II) have shown UV-Vis absorption at wavelengths ranging from 200 nm to 600 nm with the average being about 260 nm, and ethanol has a lower wavelength limit of 220 nm so it is an ideal solvent. Mercury is considered a transition metal and the molar absorptivity of bands caused by d-d transitions are relatively low, roughly in the range of 5-500 M-1 -cm1.
Sekine, T., Ishii, T. Studies of the Liquid-Liquid Partition systems. VIII. The Solvent Extraction of Mercury (II) Chloride, Bromide, Iodide and Thiocyanate with Some Organic Solvents. Bulletin of the Chemical Society of Japan. 1970. 43. 2422-2429
Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
Mercury Analysis in Environmental Samples by Cold Vapor Techniques. In: Encyclopedia of Analytical Chemistry. 2006.
Skoog , D, et al. Principles of Instrumental Analysis, 6th ed.; Brooks/Cole: Belmont, CA, 2007.
A problem thats actually very similar to mine is Chuxin Chen Analytical problem: comparative analysis of arbutin and tranexamic acid in skin whitening products. We both took an approach on cosmetics and however my approach is on a toxin found in some creams while Chuxin's is a comparative analysis between two different compounds to see which is more effective.
my analyte, Inorganic mercury, exist in many forms but the two that are most common in bleaching creams are either mercuric ammido chloride View image
and more likely mercuric chloride View image
the space filling model and the stick model of mercuric chloride are as follows View image View image
Reference for images:
I found all these images on Colombia Analytical Services (CAS) at their website; http://www.caslab.com/Mercuric_chloride_CAS_7487-94-7/
Standards for mercuric chloride could be purchased at the Sigma Aldrich website, http://www.sigmaaldrich.com/catalog/ProductDetail.do?lang=en&N4=203777|ALDRICH&N5=SEARCH_CONCAT_PNO|BRAND_KEY&F=SPEC&cm_sp=Customer_Favorites-_-Detail_Page-_-Text-203777, It sells for $99.40 the product number is 203777-50G. the CAS # is 0007487947 and since it is very toxin it must be shipped in a special poison packaging and the fee is incorporated in the price.
Posting due by 9:04 AM on Sep 30, 2011.
Recently, there has been a major interest to investigate different types of biologically produced solvents (biofuels) as substitutes for petroleum based fuels. One such biofuel that was of major importance as a transportation fuel during the First World War was butanol. Butanol has many properties that make it an ideal candidate for a petroleum substitute, most importantly being that butanol has a combustion temperature equal to that of gasoline. Meaning that butanol can fuel most of today's automobiles without a conversion to the modern engine. The biggest drawback to the use of butanol as a transportation fuel is its high cost of production.
Butanol is a fermentation byproduct of a family of Clostridia bacteria known as ABE fermenters. When provided a glucose rich feed stock this family of bacterium undergoes two lifecycles. The first lifecycle is known as acidogenesis. During acidogenesis, the Clostridia utilize glucose to produce acetic acid and butyric acid as waste products. As the two acids build up the surrounding pH in the environment lowers, when the environmental pH reaches a specific point the Clostridia switches to its second lifecycle called solventogensis. During solventogenesis, in the presence of glucose the Clostridia will then utilize the acetic and butyric acid to produce acetonitrile, butanol, and ethanol (ABE) as fermentation products. Solventogenesis will continue until all of the acetic and butyric acid has been exhausted at which point the Clostridia switches back to acidogenesis. Due to the constant switching between lifecycles, butanol is not produced continuously thus lowering the amount that can be produced leading to the high production cost.
Current research has shown that if acetic and butyric acid are initially added to the glucose feed stock the Clostridia will bypass acidogenesis and go directly into solventogenesis. Additionally, it has been shown that by changing the ratio of acetic to butyric acid will cause a change in the ratio of acetonitrile, butanol, and ethanol produced. As an analytical problem, this leads to three concerns: two are experimental and the third is engineering. The first is to determine which ratio of acetic/butyric acid will yield the highest the amount of butanol. The second: determine the rate at which the acids are utilized to determine how the acids should be continuously added to prevent exhaustion. The third is to determine or engineer a way in which the amount and ratios of two acids can be continuously monitored in the fermentation vessel in which the matrix contains glucose, acetonitrile, butanol, ethanol, acetic acid, butyric acid, and the Clostridia itself.
Lee, S., Cho, M., Park, C., Chung, Y., Kim, J., Sang, B., et al. (2008). Continuous butanol production using suspended and immobilized Clostridium beijerinckii NCIMB 8052 with supplementary butyrate. Energy & Fuels, 22(5), 3459-3464.
UV-Vis absorption spectrometry
5a. As acetic acid and butyric acid are both organic molecules it follows that all must have a UV-Visble absorbance.
Since acetic acid and butyric acid have very similar structures it would be expected that they have similar absorption properties. Using a table of common chemical constants, carboxyl groups are listed to have a wavelength maximum that should be ~205nm with a molar absortivity of ~60. Unfortunately, the table did not list solvents used to determine these values. These estimates were confirmed for acetic acid, which the NIST lists as a wavelength maximum of 207nm and a molar absortivity of 76. The NIST's website did not list the solvent used to determine this number. The NIST did list the original source for this information; however, the source was from a German journal.
Due to the relatively low wavelength maximum of these acids, it could probably be assumed that water was the most likely solvent used to determine these values. Water has a absorbance cut-off of 180nm, most alcohols have cut-offs above 260nm; additionally, both acetic acid and butyric acid are known to be soluble in water.
Skoog , D, et al. Principles of Instrumental Analysis, 6th ed.; Brooks/Cole: Belmont, CA, 2007.
National Institute of Standards and Technology. Chemistry WebBook: Acetic Acid. http://webbook.nist.gov/cgi/cbook.cgi?ID=64-19-7&Units=SI&cUV=on#Refs (accessed Sept. 28, 2011)
National Physical Laboratory. Kaye and Labby: Tables of Physical and Chemical Constants. http://www.kayelaby.npl.co.uk/chemistry/3_8/3_8_7.html (accessed Sept. 28, 2011)
I know that UV spectra data must be available for both acetic and butyric acid as these are very commonly used chemicals. I first tried to search using the KnowItAll database through the UofMN library site. When I tried to open this database, I continuously received error messages on both my home PC and a University PC. I sent Meghan an email about this and received no response; additionally, I asked her for help tracking other places to find spectral data and no response. Next, I tried searching for property data on Google. I was able to find UV spectra databases on both the University of Wisconsin and University of Texas library sites; however, I would need to be a student of those schools to access the information. After these roadblocks, I looked up my analytes on ChemSpider. ChemSpider had UV-Vis data available; except, the data is in '.jdx' format and I was unsuccessful in finding a free application I could download for this file type. My next course of action would have been to go to Walter library to find chemical encyclopedias; however, I work full-time and have two young children which makes it very difficult for me to be available during library hours. My last course of action was to find a table of common chromophores online.
6. Similar Problem: DEHP Leaching from PVC into Contents of Medical Devices
Similar Analytical Problem
a. The following problem is the most similar to mine:
DEHP Leaching from PVS into Contents of Medical Devices (Rajvi Mehta): Hypothesis- By understanding how and detecting DEHP leaching from medical devices into the body can help to prevent health risks; such as birth defects. Analytes: DEHP, Matrix: Blood/Plasma, Relevance: Health
b. Both my problem dealing with butanol production and the above problem will have a similar study in that they will need to measure changes over time. DEHP would leach slowly from the medical device. By measuring the rate that it takes for DEHP build up to harmful levels from the device will allow for a shelf-life for the device to be determined.
c. The DEHP problem differs from mine in that the location of a single analyte will change. DEHP will be moving from the medical device into the bloodstream; therefore, levels of DEHP will need to be detected and compared in both the medical device and the patient's blood stream. In my problem, the location the analytes will be found stays the same (fermentation vessel), but the analytes measured will change. While acetic and butyric acid will be detected to determine rate of change, butanol will measured as the analyte that will be built-up over time.
Blog #6 Chemical Structure and Standards
All of the standards/reagents that will be required for construction of calibration curves can be purchased through Sigma-Aldrich.
Catalog #: 338826-25ML
Catalog #: B103500-5ML
Sigma-Aldrich. http://www.sigmaaldrich.com/united-states.html (accessed Oct 24, 2011)
Blog 7: Mass Spectrometry
Mass Spectrum of Butyric (Butanoic) Acid
Blog 9: Chromatographic Techniques
1) Gas chromatography, Reverse phase LC, and HILIC would all be the most useful for separating my analytes: acetic acid, butyric acid, and butanol. Ion-exchange would not be useful as butanol typically carries a neutral charge and acetic and butyric acid would have too similar of charge to be separated. Size-exclusion is usually preformed on large molecular weight molecules(>100,000Da); all three of my analytes have molecular weights <90Da making them too small for SEC. Affinity chromatography could be used to separate butanol from the two acids as ligand beads could be produced that have affinity to carboxylic acids, but I doubt the acetic and butyric acids could be separately isolated. My analytes are not chiral or do not have r/s stereoisomers and therefore would not be applicable to chiral chromatography.
2) My first choice for separating my analytes would gas chromatography. While structurally, my analytes are similar they have different boiling points. Using the physical property of boiling point makes GC the perfect separation technique. Since, I will have large amounts of sample to work there is no need to worry about the destructiveness of the method.
3) Previous experiments utilizing GC to study butanol production have used the following column: HP-INNOwax column (Agilent Technologies Part#29091N-133LTM) Stationary Phase: bonded polyethylene glycol (high polarity); Particle Size: 0.25µm, Column Length: 30m; Column Diameter: 0.25mm; Stability Conditions: >1800°C.
4) Helium is listed as a carrier gas used for this type of experiment.
5) Previously described experiments have used a flame ionization detector. Flame ionization is suitable for hydrocarbons; which is the largest component of the three analytes in question.
Lee, S., Cho, M., Park, C., Chung, Y., Kim, J., Sang, B., et al. (2008). Continuous butanol production using suspended and immobilized Clostridium beijerinckii NCIMB 8052 with supplementary butyrate. Energy & Fuels, 22(5), 3459-3464.
Agilent Technology. HP-INNOwax Columns. http://www.chem.agilent.com/en-US/products/columns-supplies/gc-gc-mscolumns/jwhp-innowax/Pages/default.aspx (accessed Nov 10, 2011)
Power Point Presentation
Butanol Production from Clostridia Fermentation.ppt
Blog #13) Analytical Electrochemistry
1) Both acetic acid and butyric acid are electroactive. They can both be reduced to carry a single negative charge.
2) I would identify them in by using control standards to determine the E1/2 for each of the analytes.
3) I would quantify them by using control standards to create a standard curve. I would plot the limiting current versus the known concentrations of the standards. The slope of the curve would be the diffusion coefficient for the specific analyte when y-intercept is zero. Measuring the limiting current of the sample and dividing by the determined diffusion coefficient would calculate the concentration.
Skoog , D, et al. Principles of Instrumental Analysis, 6th ed.; Brooks/Cole: Belmont, CA, 2007.
Here is the link to the article that I mentioned in class today (Sep 21, 2011). Celia Arnaud, "Diagnostic Device Heads to the Field", Chemical and Engineering News, 39, August 29, 2011, page39.
The main points to stress are:
1. Solving an an analytical problem may involved developing new methods and instruments. This article mentions a great example of how to do so with limited resources.
2. How will you use the library resources to find more information about this topic (assuming that you read the hard copy)? Make sure that you have a plan on how you would proceed.
3. Detection is based on optical properties (opacity), which is different but highly relevant to instrumentation used for UV-VIS absorption.
Feel free to think outside the box when investigating your analytical problem and use creative ideas as the one described in this article.
Prions are misfolded form of proteins acting as an infectious agent, which are responsible for the transmissible spongiform encephalopathies in a variety of mammals, including bovine spongiform encephalopathy (BSE, also known as "mad cow disease") in cattle and Creutzfeldt-Jakob disease (CJD) in humans. These misfolded proteins affects the structure of the brain or the nervous system in a negative way, and is currently untreatable and fatal.
My hypothesis is that despite the aggressive regulations against the infected meat products in US, there are many countries that do not have these kind of regulation to protect public from prions, so detection of prions in such countries might help stop its spread.
This disease is transmitted by infectious meat and simple cooking does not affect these stable misfolded proteins. So the only way to avoid contracting this fatal disease is detection before its transmitted. However, detection of the infectious isoform is made difficult by the fact that it is quit similar to the normal cellular isoform of this protein.
For detecting this harmful protein few of the methods developed include FT-IR spectroscopy, nanoLC/MS/MS, and different electrophoretic methods. The analyte is usually in the blood, spinal fluids or tissue and/or bone fragments.
Onisko, B.; Dynin, I.; Requena, J.; Silva, C.; Erickson, M.; and Cartera, J. J Am Soc Mass Spectrom 2007, 18, 1070-1079
Beekes, M.; Lasch, P.; Naumann,D. Veterinary Microbiology 123 (2007) 305-319
MOMCILOVIC, D.; RASOOLY, A.; J. Food Prot., Vol. 63, No. 11, 1602-1609
UV-vis absorption spectroscopy:
The prion, my analyte in blood or serum matrix, cannot be detected on it own by UV-vis spectrometry. However, isolated prions have shown high affinity for copper ions which can make the copper prion ligand complex detectable in UV-vis spectroscopy. The article I used had different concentration of copper ions and prions used. Like for Cu(II):Prion (L) = 1:1 the maximum wavelength was 600 nm, the molar absorptivity was 140, at pH 7.3, in MOPS (40 mM) solvent. For Cu : L = 2:1 the maximum wavelength was 598 nm, the molar absorptivity was 109, at pH 7.3, in MOPS (40 mM) solvent. There were two other concentrations 3:1 and 4:1 data given in the article as well. For the 3:1 concentration the maximum wavelength was 595 nm, the molar absorptivity was 103, at pH 7.3, in MOPS (40 mM) solvent. And for the 4:1 concentration the maximum wavelength was 592 nm, the molar absorptivity was 90, at pH 7.3, in MOPS (40 mM) solvent. The article also mentioned the binding site of the prions and how the nitrate group present can reduces the Cu(II) ion to Cu(I) leading to different species formed and precipitation observed. The article talks about isolated prions but i think the same can done for detecting prions in the blood or serum sample but the concentration ratio might be different which can then be adjusted to get usable data from UV-vis spectroscopy.
Bonomo,R.; Natale, G.; Rizzarelli, E.; Tabbi, G.; Vagliasindi, L.; Dalton Trans., 2009, 2637-2646.
The analytical problem close to mine is Andrew Xayamongkhon as his matrix is also blood and it involves nitrates reacting with biological molecules present. His problem is similar to mine as we both are using the same matrix and in both our problem nitrate is reacting with the either the matrix (in his case) or copper ion (in my case) for the UV vis.
Another problem close to mine is Matt Marah - Analytical Problem: Cadmium Levels in Blood as we both are looking for harmful compounds in blood.
Similar Analytical Problems
The problems close to mine because of the same matrix blood include Nitric oxide and muscle growth (Andrew Xayamongkhon), Perfluorooctanoic acid levels in human blood (Andrew Szeliga), Cadmium Levels in Blood (Matt Marah), and DEHP Leaching from PVC into Contents of Medical Devices (Rajvi Mehta). The studies would be very different for each of these problems compared to mine and the only similarity that I think would be the blood matrix we all are using.
My problem is related to food industry and problems similar to mine according to relevance includes Nanoparticles Accumulate in the Food Chain (Nate Vetter) and I-131 in Japanese Milk Supply (Joe Zibley). The similarity in studies might include the fact that random sampling of the food products would have to be used at least for my problem and Joe's problem. The differences include the techniques used for detecting our analytes.
Hypothesis: Meat products, blood, tissues, organs, bone marrow, etc. can transmit prions, an untreatable and fatal disease, that is not only hard to detect due to very small amount of analyte present, but also unaffected by the usual methods used to cook contaminated meat or make it into meat products.
Studies: (A) Identify the regions where the prions were last officially reported, the regions most susceptible to prions outbreak - regions which use animal products in animal feed like European countries, the regions where infected products could have been shipped to unknowingly, the regions where there is no official regulations to prevent the spread of prions (developing nations like Pakistan). (B) Random sampling of the products in regions of interest and humans that report the symptoms associated with disease to detect the presence of prions. (C) Use different techniques to determine the most effective way to detect the mis-folded proteins in various matrixes (D) Investigate how far the transmission has spread over if the prions are detected in any region, by following the product supply chain and the human carriers.
The analyte concentration in a homogenate fraction is 2 micro grams per mL in a 150 mL solution. There are other concentrations of prions in different kinds of samples with the central nervous system having the highest concentration. But this concentration can be increased by different techniques before actually analyzing for prions.
Gabizon, R., MCKINLEY, M.; Proc. Natl. Acad. Sci. USA, 85 ,1988, pp.6617-6621.
Prions on its own are not fluorescent but the fluorescent dye thioflavin T (ThT) can be used to detect the prion seeding of rPrPc polymerization. The (microtiter) Polarstar or Fluostar plate reader (320 individual wells) can be used to measure THT fluorescence in relative fluorescent units (rfu) (with seeding saturation occurring at ~260,000, in the reference article). The ThT fluorescence measurements are 450 +/- 10 nm excitation and 480 +/- 10 nm emission (bottom read, 20 flashes per well, manual gain of 2000, and 20 micro seconds integration time were used in the reference analysis method). If the concentration in the sample is supposed to be quite low, the concentration of prions can be increased using protein misfolding cyclic amplification (PMCA) to dectect as little as 1 ag of PrPsc .
Wilham, J.; Orru, C.; Bessen, R.; Atarashi, R.; Sano, K.; Race, B.; Meade-White, K.; Taubner, L.; Timmes, A.; Caughey, B.; PLoS Pathogens, Vol. 6, Issue 12, 2010, pg 1-15.
Prions can be formed when the PrP 33-35 is replaced by PrP 27-30, it changes PrPc to PrPsc, the common protein to the infectious protein.
(Reference for photo 1: http://www.atsu.edu/faculty/chamberlain/Website/Lects/Prions.htm (accessed Oct 25 2011))
This causes a conformational change in the PrP protein from an a-helix to a b-sheet dominant structure. Structure 'a' is normal PrP with only alpha helix and structure 'b' is prion with beta sheets.
(Reference for photo 2: http://www.uccs.edu/~rmelamed/MicroFall2002/Chapter%2010/Prion%20Structure.html (accessed Oct 25 2011))
According to some sources the normal proteins also have beta sheets but the number of beta sheets is more in the prions.
(Reference for photo 3:
Art by Jen Philpot (accessed Oct 25 2011))
The structure of prions has not been completely identified but biologist unanimously agree that the misfolding of the protein involves alpha helix to be be replaced by beta sheets in the structure of prions.
The google search for prions standard sample did not yield any results. So for calibration the standards have to be made. This can be done using mice that are injected with 30 μl, for instance, of infected brain extract inserted into the right parietal lobe. The inocula of the mice can be of any one of the different strains of prions. The incubation time will vary depending on the strain used. The brains of these mice or its portions will be extracted and homogenized to be used as the standard. The homogenate can be prepared in phosphate buffered saline lacking calcium and magnesium ions using the infected brain tissue. The tissue will be initially dissociated using a sterile disposable homogenizer, and the suspension will be subjected to repeated extrusion through different gauge syringe needles (18 gauge and then 22 gauge). The solutions can be assayed for the desired properties, e.g. PrPsc concentration and overall prion concentration, diluted 10-fold and stored as the standards.
Stanley B.; "Prion protein standard and method of making the same", osdir.com, Patents archive.
http://osdir.com/patents/Chemistry-resins/Prion-protein-standard-method-making-06962975.html (accessed Oct 25 2011)
No, prions cannot be analyzed or quantified by atomic spectrometries directly. Prions can bind with copper so atomic absorption spectroscopy can used to show a reduction in the copper concentration and the prions can be quantified indirectly in this way. The analyte being measured is copper ions (the bound Cu(II) in the protein metal mix); absorption at 325.2 nm; the sample ashed using plasma processor TePLa 100-E (Technics Plasma), absorbed in nitric acid, and analyzed by a Zeeman 3030 (Perkin Elmer) flameless atomic absorption spectrophotometer after rapid atomization at 2000 oC in a graphite-tube cuvette HGA-70 (Perkin Elmer). Atomic absorption spectrometry was used as the concentration of Cu(II) ions is being determined in a protein-metal ion mixture and compared to the blank copper ions solution to calculate the difference in concentrations , which using absorption and Beer's law can easily be achieved.
Reference: Brown, D.; Qin, K.; Herms, J.; Madlung, A.; Manson, J.; Strome, R.; Fraser, P.; Kruck, T.; von Bohlen, A.; Schulz-Schaeffer, W.; Giese, A.; Westaway, D.; Kretzschmar, H.; Letters to Nature, Vol. 390, 1997, pp 684-687.
Blog 9: Chromatographic techniques
For separating prions gas , reverse phase, HILIC, ion-exchange, size-exclusion and affinity chromatography could be used. All these techniques are suitable for separating prions as the prions are very stable, hydrophobic and large polar molecules. Proteins are chiral too but the size and the numerous chiral centers present makes the it very difficult for prions to be separated by chiral chromatography.
Reverse phase liquid chromatography will be my first choice as it is most widely available and used chromatography technique. The availability will be useful when samples from different place can be analyzed at different labs after calibrating the equipment making the process faster.
A possible column would be AQ-C18 by SiliaChrom, with hiqh purity spherical silica, 5 micrometer particle size, 250 mm column length, 20 mm internal diameter of the column, pH stability 1.5-9.0 (possibly). The catalogue number is H151805E-Y250 and the company name is Silicycle.
The mobile phase will be 80% MeOH and 20% phosphate buffer pH 7.0.
I will use MS/MS (quadrapole/time of flight) as I expect very low levels (less than nano molar) of prions in sample if any present. This concentration can be increased using hte PMCA (protein misfolding cyclic amplification) technique but if analyzing without the amplification of prions MS/MS seems to be a good as it can detect very quantities of prions, if present.
Onisko, B.; Dynin, I.; Requena, J.; Silva, C.; Erickson, M.; Carter, J.; J. Am. Soc. Mass Spectrom., 2007, 18, 1070-1079.
Reverse phase column, http://www.gc-lc.com/column_RP.htm
My preferred technique would be nanoLC-MS/MS as it has shown ability to detect attomole quantities of prions. No one is using exactly the same technique for separation and detection but the problems with very similar techniques include "Perfluorooctanoic acid levels in human blood" (prefers LC-MS/MS); "Triclocaban in Human Urine", "Brevetoxin levels in Ocean", and "Pesticides and Toxins in fragrances and natural flavors"(all 3 prefers RPLC-MS/MS). These four prefers MS/MS but the separation techniques are a little different although they all are types of chromatography.
(I posted it as a comment first but it is still spamming my comments so I am posting in the entry too)
All the types of CE (CZE, cIEF and CGE) except for the MEKC would be suitable for separating prions from the normal proteins, and tissue, blood and bone matrixes. MEKC depends on the hydrophobicity of a molecule but the there is no known distinction in terms of sequence for hydrophobicity between prions and normal proteins yet (1). Without known difference in hydrophobicity MEKC cannot be used for separation and I was unable to find any paper using this technique for separation of prions. My first choice would be cIEF as the normal proteins have a higher isoelectric point (pI around 6.5) and the prions have a lower isoelectric point (pI around 4). This difference in the polarity allows for separation of prions even if the amount is in attomole. cIEF focusing will be performed on a Beckman P/ ACE 5500 (Beckman Instruments) controlled by P/ACE station software (Beck- man Instruments). A cIEF 3-10 Kit (Beckman Instruments) contained a neutral capillary 45 cm by 50 μm, ampholytes ranging from 3-10, and cIEF gel will be used. Markers that will be used are RNAase (pI of 9.45), carbonic anhydrase (pI of 5.98), b-lactoglobulin (pI of 5.10) and CCK flanking peptide (pI of 2.75). The catholyte solution will be 20 mM NaOH and the anolyte will be 91 mM phosphoric acid in the cIEF gel. The sample will be prepared using 4 μl of the ampholyte solution mixed with the cIEF gel and added to 5 μl of sample or makers mixed well and centrifuged at 7000 g to remove bubbles. Using a high- pressure injection for 1 min the capillary will be filled. The proteins will be focused for 2 min at a voltage of 13.5 kV. A low-pressure rinse will be applied simultaneously with the field strength of the electric field being maintained at 500 V/cm, to mobilize the focused proteins (2). The detector I would use is MS/MS as this detector can detect prions quantities as low as attomoles (3).
1. "Protein Conformation and the Concept of Misfolding", http://www.nature.com/scitable/topicpage/protein-misfolding-and-degenerative-diseases-14434929
2. Schmerr, M.; Cutlip, R.; Jenny, A. Journal of Chromatography A, 1998, 802, pg 135-141.
3. Onisko, B.; Dynin, I.; Requena, J.; Silva, C.; Erickson, M.; Carter, J.; J. Am. Soc. Mass Spectrom., 2007, 18, 1070-1079.
Prions are not electroactive as they cannot be oxidized or reduced in a quantitative manner. The prions selectively binds to copper (II) ions. This can used to quantify prions by measuring the change in absorbance by UV-vis spectroscopy with excitation wavelength at 280 nm . The beers law will be used to convert absorbance to concentration of the unbound copper ions. First get the metal free prions and determine the concentration. React the prions with cuprizone, a Cu (II) ion chelating reagent and determine the change in concentration of the cupric ions. Using this data make a calibration curve and then the curve to quantify the prions in a sample with a ion-selective.
Stockel, J.; Safar, J.; Wallace, A.; Cohen, F.; Prusiner, S.; Biochemistry 1998, 37, 7185-7193.
Most of the energy we use today comes from the combustion of oil, coal and natural gas. These fuel, when undergoing the combustion process emits a some amount of carbon monoxide (CO) due to partial oxidation of carbon-containing fuel compounds. CO is colorless and tasteless, but highly toxic. CO concentration as low as 667 ppm may cause up to 50% of the body's hemoglobin, an important complex to delivering oxygen inside the human body, to convert to carboxyhemoglobin that are unable to function as oxygen deliverer. Besides from human poisoning, CO is also one of the major urban pollutants coming from the exhaust of internal combustion engines.Thus it is important to keep track of the levels of CO in the atmosphere.
The central hypothesis is that the exhaust of internal combustion engines contains a slight amount of CO which can be collected and be analyzed in order to find the concentration of CO per volume. This value can further be used to estimate if the toxicity of the exhaust of the fuel. Thus the analyte is CO and the matrix it is found is a mixture of sulphur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO) and carbon dioxide (CO2).
1. Omaye ST. Toxicology, 2002,180 (2), 139-150.
2. Tikuisis, P; Kane, DM; McLellan, TM; Buick, F; Fairburn, SM. Journal of Applied Physiology. 1992, 72 (4): 1311-1319.
3. Z.M. Ao; J. Yang; S. Li; Q. Jiang. Chemical Physics Letters. 2008, 461(4-6), 276-279.
UV-Vis absorption spectrometry
a) CO has been reported in the literature to have absorptions from around 70nm to 200nm and shows various peaks and intensities. In general, these absorption spectrum was taken in the gas phase thus no solvents was used though the gas pressure of the absorption cell differs from case to case.
b) According to Myer and co-workers, CO has an absorption cross section value of near 5Mb at 107~108nm, several other peaks were also observed with absorption cross section value of 3Mb at around 150nm. Huffman and co-worker reported a relatively strong absorption peak at 79nm with an absorption coefficient value of near 1900cm-1 in the 60-100nm region.
4. R.E. Huffman, J.C. Larrabee, Y. Tanaka. Absorption Coefficients of Carbon Monoxide in the 1006-600-Å Wavelength Region. J. Chem. Phys. 1964, 40, 2261-2269.
5. J.A. Myer, J.A.R. Samson. Vacuum-Ultraviolet Absorption Cross Sections of CO, HCl, and ICN between 1050 and 2100 A. J. Chem. Phys. 1970, 52 (1), 266-271.
6. C. Letzelter, M. Eidelsberg, F. Rostas, J. Breton, B. Thieblemont. Photoabsorption and photodissociation cross sections of CO between 88.5 and 115 nm. Chem. Phys. 1987, 114, 273-288.
7. H. P. White, Xin-Min Hua, J. Caldwell, F. Z. Chen, D. L. Judge, C. Y. R. Wu. The Ultraviolet Absorption Spectrum of CO: Applications to Planetary Atmospheres. J. Geophys. Res. 1993, 98(3), 5491-5497.
Similar Analytical Problem
Lauren Sauer, "Vapor intrusion in buildings". Analyte type: Trichloroethylene and Tetrachloroethylene(Gas). Matrix type: Air (Gas). Relevance: Environmental, Health.
Studies that are similar will be the sampling of the air. Since the analyte's concentration is low, there might be extraction steps that will be alike.
Studies that are different: In my problem I might need to control the concentration of oxygen and look at the corresponding amount of CO in the exhaust. Her study would control the distance from the industrial plants where the air sample is taken.
Insecticide aerosol is commonly used in Malaysia. Every household in Malaysia uses insecticide aerosol almost everyday especially in some rural areas. It is known that liquefied petroleum gas is one of the chemicals present in an aerosol as to replace the use of CFC. However, LPG is slightly harm to our health and environment. But, the frequent use of insecticide aerosol might be harmful to health if no precautions taken. Some serious cases, inhalation of too much LPG will cause asphyxiate, which not everyone are aware of. Therefore, my analytical problem is to determine the amount of LPG in insecticide aerosol so as to control the amount of the insecticide that can be used and accordingly. The matrix would be the solvent that is used to dissolve LPG in the insecticide aerosol, where kerosene is one of it.
MSDS of LPG: www.hvacredu.net/gas-codes/module2/LPG_MSDS.pdf
S Prasad, Ruchi Singh, Rajesh Manocha, M Narang, BD Sharma, P Rajwanshi, B Gupta. Acute Massive Rhabdomyolysis Due to Inhalation of LPG. JAPI. 2009, 57, 472-473.
Similar Analytical Problem:
Lauren Saurer - Vapor Intrusion in Building
Similarity: our studies focus on the quality of indoor air and focuses on to quantitatively determine the presence of analyte of interest in the indoor air of affected surrounding.
Difference: her analytes of interest are single compounds whereas my analyte might have different composition from different sample depending on the manufacturer. So, in my study, I need to identify the characteristic of my analyte in the samples first before I'm able to quantitatively determine the analyte.
My preferred technique is gas chromatography with split flame ionization/ electron capture detection. Other analytical problems that use same techniques "Silicones in Cosmatics" by Melissa which uses GC/MS, "Vapor Intrusions in Building" by Lauren which uses GC/FTMS, and "Butanol Production from Clostridia Fermentation" by David which uses GC with FID detector.
My analytical problem is about polymer solar cells. Currently, silicon based solar cells are widely used when it comes to solar cells. Many researches are being done regarding polymer solar cells because they offer some advantages. The cost to manufacture polymer solar cells is lower(1). Besides that, polymer solar cells are flexible(1). They may be used in clothes(1). Polymer based solar cells would also be lighter because polymer is like plastic. Unfortunately, the current polymer solar cells have a short life span(1). The presence of air and changes in temperature shortens the life time of polymer solar cells(2). Illuminations as in light or dark tend to degrade the polymer solar cell as well(1). My central hypothesis is to increase the life span of polymer solar cells. The main analyte are polymers. The matrix would be the solvent where the polymer is dissolved in.
1) Rasmus, Larsen, Petersen and Lund. Polymer solar cells. Aalborg University. (2006)
2) Janssen. Introduction to polymer solar cells. Eindhoven University of Technology, The Netherlands.
UV-Vis absorption spectrometry.
I am going to refine my hypothesis. I am focusing on the morphology of solar cells. Morphology is the study of the architectural structure of the polymer. If morphology can be improved, the life span of solar cells can be improved. In solar cells, two types of polymer would be mixed in a solution and spin-cast. The solution may evaporate and the remaining polymers act as charge donor and charge acceptor respectively. It had been found that the efficiency of solar cell has increased when chlorobenzene used as solvent instead of toluene. UV-Vis absorption spectrometry can be used to identify if any interactions happen between the polymers and solvent. The maximum wavelength value of chlorobenzene for UV-Vis absorption spectrometry is 310nm. If the wavelength seems to vary, then interaction between the solvent and the polymers can be suspected. Other than that, whenever, the polymer gives out charge, they tend to crumpled up among it self. Meaning the interaction between the two polymers seems to be decreasing. This can be observed using transmission electron microscopy (TEM). When the interaction between both of the polymers decreases, the solar cell can no longer be used. The key to improve the life span of solar cell is to maintain the polymers from crumpling up to it self respectively. The polymer pairs that are commonly used are P3HT/PCBM and MDMO-PPV/PCBM.
Thompson, B. C.; Frechet, J. M. J.; Polymer-Fullerene Composite Solar Cells. Angew. Chem. Int. Ed. 2008, 47, 58-77
For some reason my comment on F-9- Reduction of Mesotrione in Aquifers and Surface Waters doesn't appear. So, I'll post my comment here:
This analytical problem is almost similar as mine because in this problem, the pseudo-steady state reactivity is being studied. In my problem, I would like to maintain a good morphology of the polymers. Meaning I would like to find ways where the polymers would be stable and would not degrade by crumpling up to itself respectively. Besides that, in this problem transmission electron microscopy has been used. And I am also planning to use that method to investigate my problem.
Similar Analytical Problem.
Matt Wasilowski-Analytical Problem-Biodiesel from waste water sludges.
I believe the above mentioned analytical problem would be slightly similar to mine. The analytes being studied in this problem are lipidic material present and the biodiesel monoalkl ester of interest. These analytes are found in the matrix of original filtered waste water feedstock and the final product stream.
I believe this problem is slightly similar to mine because it involves Green Chemistry. In this problem, methods are developed to find ways to reuse waste water. I believe this would be beneficial to the environment. In my problem, I'm trying to increase the life span of polymer cells. If polymer solar cells are widely used one day, I believe it would be an alternative way to get clean energy. This corresponds to Green Chemistry.
The studies would be different in the sense that, the analyte in the above problem, are organic materials while in my problem they are polymers.
1. Hypothesis: Morphology of P3HT/PCBM depends on the ratio they are prepared in and the temperatures they are in.
Studies: (A) Determine the highest temperature that P3HT and PCBM could withstand. (B) Prepare solutions of them with different weight ratios (ex: 1:1, 1:2, 1:4, etc) and spin cast them. Heat them up at different temperatures. Then cool them down at different temperatures to see if there are any changes to the morphology. (C) Identify the blend ratio that is most stable with the largest range of temperatures. (D) Find the maximum and minimum temperatures at which the selected blend ratio would be stable.
2. ITO coated glass would be cleaned. Solution of P3HT/PCBM would be prepared in various weight ratios in chlorobenzene. Then the solution would be spin cast on the glass. Therefore, the analyte would be occupying the most space on the glass. In case the solvent does not dry out completely, that might become part of the matrix. But, I don't think that would be the case because the solvent should all be evaporated during spin-cast. Other than that, the glass where the solution would be spin-cast would be the background.
I forgot to put the reference when I answered the previous blog. Here is the reference:
Vanlaeke, P.; Swinnen, A.; Haeldermans, I.; Vanhoyland, G.; Aernouts, T.; Cheyns, D.; Deibel, C.; D'Haen, J.; Heremans, P.; Poortmans, J.; Manca, J.V. P3HT/PCBM bulk heterojunction solar cells: Relation between morphology and electro-optical characteristics Solar Energy Materials & Solar Cells 90 2006, 2150-2158.
Based on the papers I have read so far, I have not come across fluorescence method being used to study P3HT. Therefore, I am answering #4 for this blog.
In the FTIR spectrum, the thiophene ring that corresponds to P3HT shows out of plane deformation of C-H at 819cm-1 (wavenumbers). This is used to study the charge transfer effect in P3HT. A new band develops at 835cm-1 for the 1:1 P3HT:PCBM film. When the amount of PCBM is increased, the intensity of the band increases as well. This band is due to the charge transfer between sulfur atom from P3HT molecule to PCBM molecule. Therefore, the bands that I should be looking for in IR spectrum would be the bands at 819cm-1 and 835cm-1. Besides that, I should be taking the IR of P3HT and PCBM on their own and the IR once I have mixed them in the ratio of interest. Later on, the IR of this mixture would be taken at different temperatures. And these IR spectrums can be compared to the IR spectrum of P3HT (on its own), PCBM (on its own), and the pristine mixture that was initially prepared to observe any changes that may occur on the spectrum.
Shrotriya, V.; Ouyang, J.; Tseng, R. J.; Li, Gang.; Yang, Y. Absorption spectra modification in poly(3-hexylthiophene):methanofullerene blend thin films Chemical Physics Letters 411 2005 138-143
2. This is poly(3-hexylthiophene-2,5-diyl). It is commonly abbreviated as P3HT. In a polymer, this molecule is repeated creating a chain like structure. This is Phenyl C 61 butyric acid methyl ester. It is commonly abbreviated as PCBM.
3. I do not think I would need to calibrate my instrument. The spectrum that I would take with each sample would be compared to the spectrum of the sample when it was initially prepared.
Company that sells P3HT and PCBM: Sigma Aldrich
P3HT: Product number: 445703-1G; Quantity: 1g in glass bottle; Price: $590.00
PCBM: Product number: 684457-100MG; Quantity: 100mg in glass bottle; Price:
The analyte that I would be looking at mainly is P3HT. Its molecular weight is not really fixed. People had studied the temperature dependent x-ray diffraction and reflectivity measurements using rr-P3HT with molecular weight of 45000 g/mol. The mass analyzer I would be using is MALDI-TOF. Example of mass spectrum:
MALDI-TOF mass spectrum of regioregular P3HT-NH2
Xu. Jun; Wang. J; Mitchell. M; Mukherjee, P; Jeffries-EL. M; Petrich. J; Lin. Z. Organic-Inorganic Nanocomposites via Directly Grafting Conjugated Polymers onto Quantum Dots J. AM. CHEM. SOC. 2007, 129, 12828- 12833
Size exclusion chromatography would be the most preferred method. This chromatography is best for analyzing proteins, polymers, and generally any big sized molecules. The column would be used is a mixed-C PL-Gel (PL) column. This column could be purchased from Thomas Scientific. Its manufacturing number is 79911GP-110. It costs $677.08/ EA. Detector would be used is Refractive Index detector (Shodex).
1) S. Bertho et al. / Organic Electronics 10 (2009) 1248-1251
2) Journal of The Electrochemical Society, 156 _4_ K37-K43 _2009_
3) Macromolecules, Vol. 43, No. 10, 2010
1. Preferred technique: UV-Visible spectroscopy.
2. Analytical problems that have selected the same technique: Nanoparticles Accumulate in the Food Chain, Comparative analysis of arbutin and tranexamic acid in skin whitening products, Nitric oxide and muscle growth.
The best type of CE for my problem is CGE because I am dealing with polymers. CZE is good for protein. CIEF is normally used for proteins and peptides.
Buffer used is PEDOT:PSS layer. Its pH range is 1 to 2. Capillary used would be coated capillary.
The detector would be used is absorption spectrometry. This is because P3HT and PCBM have been usually monitored using their absorption.
Elschner, A., Kirchmeyer, S., Lovenich, W., Merker, U., Reuter. Knud., PEDOT Principles and Applications of an Intrinsically Conductive Polymer; Taylor & Francis Group, LLC, Florida, 2011; p 220.
Since P3HT and PCBM are involved in solar cell, they should be electroactive. Galvanic cell could be used to identify P3HT and PCBM when they transfer electrons to each other.
The use of plastics for the development and fabrication of medical devices has increased recently, the most used plastic being poly(vinyl chloride) (PVC). A phthalate ester plasticizer that is used to make PVC soft and flexible, di-2-ethylhexyl phthalate (DEHP), has been leaching from medical tubing and blood bags and into the contents of the tubing and/or bags. For example, some patients have received transfusions of stored blood containing detectable amounts of the plasticizers, and even some that migrated from medical tubing used for dialysis may have been associated with hepatitis-like symptoms that were seen in many dialysis patients.
It was shown that with a longer storage time, there was a larger accumulation of DEHP in the contents of the medical devices. Large amounts of DEHP can cause a variety of symptoms and diseases, including birth defects, decreased fetal weight, miscarriages, and liver cancer. The EPA has classified vinyl chloride as a Group A human carcinogen.
Manufacturers of these blood bags seem to adhere to the USP requirements for plastics testing, but these tests seem to have overlooked the presence of or migration of the DEHP from the plastics into the contents, which seems to indicate that a method should be used with a lower Limit of Detection.
My hypothesis is that with continued exposure to DEHP, many more adverse health effects could manifest and be detrimental to the human body. By analyzing samples of blood and plasma (the matrices in which the analyte can be found), the amount of DEHP (the analyte in question) that leaches from the PVC into the contents can be ascertained, and perhaps an alternative can be found. (1)
UV-Vis Absorption Spectrometry
The maximum wavelength of absorption for my analyte, DEHP, is 270 nm. The solvent used for the determination of this wavelength was hexane. (2) I was unable to find a value for the molar absorptivity of DEHP. I was going to attempt to calculate it, based on information given in another paper (3), but unfortunately, they did not give a path length used, and because of this, I was unable to calculate a value.
-Similar Analytical Problem (in case it doesn't show up in the comments):
The analytical problem that I think most resembles mine is the one with PFOA and Teflon. In this problem, PFOA is a surfactant that persists after it leaches out of Teflon, which can be compared with the DEHP plasticizer that leaches out of PVC. PFOA is also a carcinogenic, and DEHP has adverse effects that can be equally harmful to the human body.
Similar Analytical Problem
The analytical problem that is the most similar to mine is the one involving Teflon and PFOA. Megan Hartmann is the student that is presenting this topic. Her problem consists of PFOA leaching from the Teflon used to make pots and pans, and PFOA is carcinogenic and is therefore detrimental to human health. Megan's analyte is PFOA and her matrix is the air around Teflon pots and pans after they've been scratched, to see if any PFOA is released.
I think the studies that need to be done for our problems will be quite different. I am going to be measuring DEHP accumulation over time and so I will need to collect samples of blood and plasma that have been stored in medical devices made with PVC for varying periods of time, to show the relationship between accumulation over time. Megan will be testing to see if PFOA is released from Teflon; I don't think her analytical problem has any time dependence, and so she will not need to take samples over time. I think she only will be taking samples from different pots and pans made of Teflon. For my analytical problem, a negative control would be a sample from a medical device that is not made with PVC, and a positive control would be a sample from a medical device that is made with PVC. Megan's controls would be slightly similar; her negative control would be a sample from cookware that is not made with Teflon, while her positive control would be a sample from cookware that is made with Teflon.
Studies Needed to Investigate the Analytical Problem
Hypothesis: DEHP accumulates over time and can cause many adverse health effects that can be detrimental to the human body, such as liver cancer.
Studies: (A) Identify medical devices fabricated with PVC. (B) Measure DEHP accumulation levels in blood and plasma stored in said devices over time. (C) Measure DEHP accumulation levels in blood and plasma stored in medical devices that are (a) known to be made using DEHP, as a positive control, and (b) not made using DEHP, as a negative control.
Analyte Levels in the Matrix: In the range of 24 to 72 hours, the DEHP levels in platelet concentrates ranged from 76-491 µg/mL, the levels in platelet rich plasma ranged from 34-181 µg/mL, and the levels in platelet poor plasma ranged from 52-285 µg/mL. (4)
Even after checking various handbooks and sifting through the literature, I was unable to find maximum excitation and emission wavelengths for DEHP. From the molecular features of the compound, however, I would speculate that DEHP fluoresces naturally. It has an aromatic group in conjugation with two carbonyl groups, and so the pi electrons can easily move around, creating resonance. To determine the maximum excitation wavelength, I would pick any emission wavelength, and then scan all the excitation wavelengths until the maximum was found. After this, the maximum excitation wavelength will be fixed, and the emission wavelengths will be scanned until that maximum is found.
I would choose to use a spectrofluorometer for the analysis of my analyte. I choose this over a fluorometer because I will need to scan multiple wavelengths to determine my maximum excitation and emission wavelengths. Also, I will only be analyzing small samples of my analyte at a time, so using a standard instrument would be okay.
Chemical Structure and Standards
The DEHP standard that I will need to use can be purchased from Sigma-Aldrich. The catalogue number is 36735, and it is available only in 1 g quantities, which cost $27.90.
Atomic and Mass Spectrometries
Atomic spectrometries cannot be used for the detection of my analyte because it is not a chemical element.
Mass spectrometry can definitely be used for the detection of my compound. My compound is di(2-ethylhexyl) phthalate, or DEHP. Its nominal mass is 391 Da and its exact mass is 390.277 Da. One of the methods I could use for mass spectrometry would include ESI as the ionization source and single quadropole for the mass analyzer. The literature source doesn't directly say that this mass analyzer is the one, but it was determined after searching for the instrument they used (5). The second method that I could use would use API as the ionization source and QTrap for the mass analyzer (6).
Mass Spectrum of DEHP (6)
This sample preparation procedure is for use in LC:
(1) Centrifugation: The whole blood was centrifuged at 4,200g for 10 minutes, making PPP (platelet-poor plasma.
(2) Extraction: 1mL of PPP was removed from PVC bags and extracted with 3mL of acetonitrile, 1mL of NaOH (1 N), and 100 µL of an internal standard solution.
(3) Centrifugation II: Shake for 5 minutes, and then centrifuge at 4,000g for 10 minutes.
(4) The supernatant is then injected onto the column. (7)
From the types of chromatography covered in class, I think that RPLC, HILIC, and GC would be the only viable options. My analyte, DEHP, doesn't carry a net charge, which means that ion-exchange will not work; it is too small for SEC; it won't have a specific affinity for anything in particular, which means that affinity chromatography will not work; and I will not need to separate it from its diastereomers, which means that chiral chromatography will not work.
RPLC would be my first choice to separate my analyte from other matrix components due to the nonpolar nature of the column used.
A commercial column used was purchased from VWR International. It is a C18 LICHROSPHER column, with a particle size of 5µm, a length of 125mm, and an inner diameter of 4mm. The catalogue number is 48219-354, and the price is $712.13. (8)
The mobile phase used for a separation utilizing the previous column was a 15:70:15 mixture of water:acetonitrile:THF. (8)
The detector suggested was a UV detector, but I think a fluorescence detector would be a better idea. My analyte is naturally fluorescent, and so would be easier to detect. Fluorescence is more sensitive than UV-Vis, and so it might be easier to differentiate between DEHP and its monoester metabolite, MEHP. Since fluorescence is more selective, it will remove other interferences from the matrices, blood and plasma.
Capillary Electrophoresis Techniques
Out of all the CE techniques that we covered in class, I think MEKC and CGE would be suitable to separate my analyte from other matrix components. Since DEHP is neutral, in MEKC it would separate from the other neutral components. CGE, which is a separation based on size, would separate DEHP from the other components in the blood and plasma matrices, including proteins of various sizes. CZE would not be suitable, because CZE is a separation based on charge and size, and as my molecule is neutral, it will not separate and will just stay with the EOF. cIEF is a separation based on different pIs. The pI of a molecule is the pH at which the molecule has a net zero charge, which could also mean that the positive and negative charges are balanced. Because DEHP is neutral and has no ionizable groups, it won't have a pI. When the voltage is applied, I think it would simply diffuse throughout the separation media rather than focusing.
MEKC would be my first choice for the CE technique that is most suitable for the separation of DEHP from other matrix components. The addition of a surfactant to the buffer in MEKC aids the formation of micelles, which have both hydrophobic and hydrophilic components. Thus, the hydrophobicity of the analyte plays a large role. Since DEHP is neutral and hydrophobic, it can partition into and out of the micelle and be separated from other neutral components, since while it is in the micelle, it has the same electrophoretic mobility as the micelle. It is also spending a different amount of time in the micelle compared to other neutral components due to varying affinities.
In the first paper I found, the buffer composition was SDS dissolved in a mixture of 0.02M sodium dihydrogen phosphate solution and 0.02M sodium tetraborate solution adjusted to a pH of 9.0. An electric field of 5-30kV was applied between the platinum electrodes that were in the carrier solution. The capillary used was fused silica that was 720mm long, with an inner diameter of 50 μm. On-column detection was used by UV Absorption at 210nm. The detector was placed 500mm from the positive end of the capillary. Samples were injected by vacuum injection (5 in. of Hg for 0.2s) and the injection volume was 1.5nL. (9)
In the second paper I found, the buffer composition was 100mM sodium cholate (SC), 50mM borate, and 15% methanol. The pH was 8.5. The applied electric field was 20kV. The capillary used was a fused silica capillary, with a total length of 60cm, an inner diameter of 75μm, and an outer diameter of 375μm. On-column detection was used by UV Absorption at 214nm. The detector was placed 50cm from the beginning of the capillary. Samples were injected by using a pressure of 3.5kPa (0.5 psi) for 3s. In this paper, they added PEG-400 to modify the micellar phase. When PEG-400 was increased from 0-5% in the same buffer, an increased resolution of DEHP was observed. When 2% PEG-400 was used, baseline separation of all the phthalates in the study was observed. Methanol and acetonitrile were also used to optimize the separation of the phthalates. A baseline separation was achieved when 15% methanol or 30% acetonitrile was added to the original buffer. (10)
In another paper found, the concentrations of DEHP in whole blood was, on average, 0.0238mg/mL (11). The limit of detection for MEKC in the second paper found was 0.054mg/L (10). This LOD is far lower than the concentrations that are observed in samples containing DEHP, and so I think that the on-column UV Absorption detectors used in both of these papers are sufficient for the analysis at hand.
It has been shown that aliphatic phthalate esters are reducible at highly negative potentials (about -1700mV). This reduction was shown at a hanging drop mercury electrode to have a two-step mechanism, corresponding to each of the current-voltage curves observed when using Normal Pulse Polarography (NPP) (12). This reduction is not reversible (12,13).
Each phthalate ester was shown to have a unique E1/2 value compared to the S.C.E. when using NPP, therefore if a standard of DEHP were tested, its E1/2 could be used for identification. Typical E1/2 range is -1600mV to -1800mV (12,13). In another paper, phthalate esters were analyzed using Differential Pulse Voltammetry (DPV) with a hanging drop mercury minielectrode, showing unique peak currents at respective E1/2 values. Again, DEHP standards can be used to distinguish DEHP from other phthalates (14).
Both NPP (13) and DPV (14) can be used for quantitation, since wave height in NPP and peak currents in DPV are proportional to the analyte concentration. Standard curves can be readily constructed showing strong linearity (14) and sensitivity in the low to sub μM range (better than HPLC-UV) and can be further improved to the nM range when preconcentration with SPE is done.
1.Jaeger, R.J.; Rubin, R.J. Migration of a Phthalate Ester Plasticizer from Polyvinyl Chloride Blood Bags into Stored Human Blood and its Localization in Human Tissues. New Engl. J. Med. 1972, 287, 1114-1118.
2. Aignasse, M.F. ; Prognon, P. ; Stachowicz, M. ; Gheyouche, R. ; Pradeau, D. A New Simple and Rapid HPLC Method for Determination of DEHP in PVC Packaging and Release Studies. Int. J. Pharm. 1995, 113, 241-246.
3. Yu, B.Y. ; Chung, J.W. ; Kwak, S. Reduced Migration from Flexible Poly(vinyl chloride) of a Plasticizer Containing β-Cyclodextrin Derivative. Environ. Sci. Technol. 2008, 42, 7522-7527.
4. Rock, G. ; Labow, R.S. ; Tocchi, M. Distribution of Di(2-ethylhexyl) Phthalate and Products in Blood and Blood Components. Environ. Health Perspect. 1986, 65, 309-316.
5. Inoue, K. ; Higuchi, T. ; Okada, F. ; Iguchi, H. ; Yoshimura, Y. ; Sato, A. ; Nakazawa, H. The Validation of Column-Switching LC/MS as a High-Throughput Approach for Direct Analysis of Di(2-ethylhexyl) Phthalate Released From PVC Medical Devices in Intravenous Solution. J. Pharm. Biomed. Anal. 2003, 31, 1145-1152.
6. Ito, R. ; Seshimo, F. ; Miura, N. ; Kawaguchi, M. ; Saito, K. ; Nakazawa, H. High-Throughput Determination of Mono- and Di(2-ethylhexyl) Phthalate Migration from PVC Tubing to Drugs Using Liquid Chromatography-Tandem Mass Spectrometry. J. Pharm. Biomed. Anal. 2005, 39, 1036-1041.
7. Dine, T. ; Luyckx, M. ; Cazin, M. ; Brunet, C. ; Cazin, J.C. ; Goudaliez, F. Rapid Determination by High Performance Liquid Chromatography of Di-2-ethylhexyl Phthalate in Plasma Stored in Plastic Bags. Biomed. Chromatogr. 1991, 5, 94-97.
8. Bourdeaux, D. ; Sautou-Miranda, V. ; Bagel-Boithias, S. ; Boyer, A. ; Chopineau, J. Analysis by Liquid Chromatography and Infrared Spectrometry of Di(2-ethylhexyl) Phthalate Released by Multilayer Infusion Tubing. J. Pharm. Biomed. Anal. 2004, 35, 57-64.
9. Takeda, S. ; Wakida, S. ; Yamane, M. ; Kawahara, A. ; Higashi, K. Migration Behavior of Phthalate Esters in Micellar Electrokinetic Chromatography With or Without Added Methanol. Anal. Chem. 1993, 65, 2489-2492.
10. Guo, B. ; Wen, B. ; Shan, X. ; Zhang, S. ; Lin, J. Separation and Determination of Phthalates by Micellar Electrokinetic Chromatography. J. Chromatogr. A. 2005, 1095, 189-192.
11. Valeri, C.R. ; Contreras, T.J. ; Feingold, H. ; Sheibley, R.H. ; Jaeger, R.J. Accumulation of Di-2-ethylhexyl Phthalate (DEHP) in Whole Blood, Platelet Concentrates, and Platelet-Poor Plasma: 1. Effect of DEHP on Platelet Survival and Function. Environ. Health Perspect. 1973, 103-118.
12. Whitnack, G.C. ; Reinhart, J. ; Gantz, E.S.C. Polarographic Behavior of Some Alkyl Phthalate Esters. Anal. Chem. 1955, 27, 359-362.
13. Whitnack, G.C. ; Gantz, E.S.C. Polarographic Determination of Phthalate Esters in Plastics. Anal. Chem. 1953, 25, 553-556.
14. Qureshi, M.S. ; Fischer, J. ; Barek, J. ; Sirajuddin ; Bhanger, M.I. Voltammetric Determination of Aliphatic Phthalate Esters at a Hanging Mercury Drop Minielectrode and a Meniscus Modified Silver Solid Amalgam Electrode. Electroanal. 2010, 22, 1957-1962.
Surfactants are a class of organic compounds that are frequently utilized as emulsifiers and stabilizers in the formulation of consumer based cosmetic products. Examples include the anionic surfactants sodium lauryl sulfate and sodium octanesulfonate. These compounds are often incorporated into cleaning agents, shampoos and toothpastes with the purpose of facilitating and stabilizing oil/water emulsions.(1)
These compounds are used in large scale by consumers in the personal care product market, and therefore it is within the realm to assume that detection and treatment of water sources contaminated by surfactants is a necessary and frequent occurrence.
After the Deepwater Horizon catastrophe that occurred last spring, the EPA forced the BP oil company to expedite their decision on choosing a dispersant agent to clean up the oil slick covering a large portion of the Gulf of Mexico. Even with the possibility of using a wide array of safer alternatives, the Corexit® "sulfate surfactant "product line of dispersants was chosen by BP, in spite of the knowledge of its toxic effect on both human health and marine life. (2)
Even though the chemical composition for Corexit® has been kept a trade secret for many years, the EPA required its disclosure with the purpose of creating a life cycle assessment for the mixture that was introduced in large quantities in and around the Mississippi delta. Large amounts of the anionic surfactant Dioctyl sodium sulfosuccinate revealed to be a part of the Corexit® mixture. This compound has a wide variety of environmental and biological issues due to its known toxicity. These issues include human health concerns along with contamination and biological disruption of freshwater and marine life. Methods are currently being researched that will hopefully allow the detection of concentration of dioctyl sodium sulfosuccinate efficiently in an oceanic matrix. (3) An image of DOSS is shown below. (8)
Dioctyl sodium sulfosuccinate (CAS 577-11-7) can be purchased from Sigma-Aldrich in the form of a salt at 96% purity. Their product number is D201170. A purchase of 100g can be made for 28.00 USD. (9)
I would like to focus my efforts to research the various methods that are currently practiced in the analytical field to detect and characterize anionic surfactants as contaminants in water sources. Thus far, methods for detecting anionic surfactants that I have read about include
-Liquid Chromatography (4)
-Fluorescent absorption of attached dies (5)
-Chromo- and fluorogenic colorimetric detection (6)
-Ion pair chromatography (7)
The analyte(s) frequently used for these established methods have consisted of linear alkyl chains attached to anionic head groups, since these types of surfactants are most prevalent in consumer based products. I will therefore focus my interest on the detection of anionic, straight chained molecules such as sodium lauryl sulfate and/or sodium octanesulfonate in a water matrix. Hopefully after decent exploration into the subject matter, I will be able to make some assumptions and obtain some insight on an analytical method that may be utilized to detect dioctyl sodium sulfosuccinate in an oceanic matrix.
My hypothesis is that a similar method to those mentioned above can be used, but the process will have to be tweaked to account for the branched nature of dioctyl sodium sulfosuccinate and the other dissolved compounds found in an oceanic matrix. My revised hypothesis is that anionic surfactants should be present in higher concentrations in areas that have been exposed to dispersant chemicals compared to other natural water sources with with no known history of intentional contamination.
My hypothesis that the presence of Dioctyl sodium sulfosuccinate (DSS or DOSS) along with other anionic surfactants that are found in the Corexit dispersant, are still be migrating throughout the Gulf of Mexico with the oil that was not accounted for during its recovery process.
Since migrating oceanic species, such as dolphins and sea turtles, have known toxicology issues to petroleum and surfactants, if one were to take water samples from varying radial regions where these migrating sea animals corpses have been found on the coast of the Gulf, DOSS will be detected.
(1) Kosswig, K. In Surfactants; Ullmann's Encyclopedia of Industrial Chemistry; Wiley-VCH Verlag GmbH & Co. KGaA: 2000
(2) Eilperin, J. Post Carbon: EPA demands less-toxic dispersant. The Washington Post [Online] May 20, 2010. http://views.washingtonpost.com/climate-change/post-carbon/2010/05/epa_demands_less_toxic_dispersant.html. (accessed Sept 19, 2011).
(3) Schor, Elana. Ingredients of Controversial Dispersants Used on Gulf Spill Are Secrets No More. The New York Times [Online] June 9, 2010. http://www.nytimes.com/gwire/2010/06/09/09greenwire-ingredients-of-controversial-dispersants-used-42891.html (accessed Sept 19, 2011).
(4) Boiani, J. Spectator ion indirect photometric detection of aliphatic anionic surfactants separated by reverse-phase high-performance liquid chromatography. Anal. Chem. 1987, 59, 2583.
(5) Qian, J.et al. Selective and sensitive chromo- and fluorogenic dual detection of anionic surfactants in water based on a pair of "on-off-on" fluorescent sensors. Chemistry - A European Journal 2009, 15, 319.
(6) Coll, C. et al. A simple approach for the selective and sensitive colorimetric detection of anionic surfactants in water. Angewandte Chemie (International ed.in English) 2007, 46, 1675.
(7) Ding, W. et al. Determination of linear alkylbenzenesulfonates in sediments using pressurized liquid extraction and ion-pair derivatization gas chromatography-mass spectrometry. Anal. Chim. Acta 2000, 408, 291.
(8) Dioctyl sodium sulfosuccinate. http://upload.wikimedia.org/wikipedia/commons/thumb/d/d5/Dioctyl_sodium_sulfosuccinate.png/320px-Dioctyl_sodium_sulfosuccinate.png (accessed Oct 26, 2011).
(9) Dioctyl sulfosuccinate sodium salt 96%. Sigma-Aldrich. http://www.sigmaaldrich.com/catalog/ProductDetail.do?D7=0&N5=SEARCH_CONCAT_PNO%7CBRAND_KEY&N4=D201170%7CALDRICH&N25=0&QS=ON&F=SPEC (accessed Oct 26, 2011).
UV-Vis absorption spectrometry
Anionic surfactants must be coupled with specific dyes in order to be detected by UV/Vis spectrometry. The dyes are the actual molecules that are being detected by UV/Vis, and not the surfactant itself. According to Yuxiu An, et al (10), their group was successful in detecting Sodium Lauryl Sulfate both in the UV and Visible spectrum. The dyes used in the experiment were the compounds:
With major absorptions found at 532 and 409 nm, respectively
Their method has an keen advantage because the presence of the specific surfactant could be detected qualitatively by a color change in solution (yellow to pink), along with a quantitative measurement by UV absorbance with a detection limit in the order 10^-9 M.
The only issue that was found was the inability of their chosen dyes to couple with shorter carbon chained surfactants, specifically octyl sulfates. The assumption was that the sterics of the short chained surfactants limited the stoichiometric dissociation of the the dyes, giving varied experimental results for known standard concentrations of surfactants dissolved in aqueous solutions. I feel as if this method still has potential, but specific types of dyes must be found/synthesized that will selectively couple to shorter chained surfactants without any steric interaction.
(10) Yuxiu A. et al. Disassembly-driven colorimetric and fluorescent sensor for anionic surfactants in water based on a conjugated polyelectrolyte/dye complex. Soft Matter. 2011, 7, 6873.
After searching the blog, I found that Joe Zibley's analytical problem, entitled I-131 in Japanese Milk Supply , is quite similar to my problem in question. Please read his posting and my comments thereafter to understand my reasoning.
update 9/29 at 6:15PM
My comment post does not seem to be showing up on Joe's blog post. In summary...
I found our analytical problems similar in nature because we are both require to use some type of coupling reagent that will make our analyte detectable in the UV/Vis spectrum. Also both of our analytes in question are found in an aqueous matrix.
Our problems differ however, in the fact that his analyte is a radioactive element, while mine is a low molecular weight, anionic chemical compound.
Similar Analytical Problem
Erik Sahlin's analytical problem involving Brevetoxin levels in the ocean I found most similar to mine. His hypothesis is that one can detect the amount of Brevetoxin levels in certain oceanic areas based upon the concentration of Brevetoxin found in dead fish that have been washed up on shore. His analyte/matix is obviously brevetoxin in the ocean.
I found this problem similar to mine in that both of our analytes are of a toxicity concern to both marine wildlife and human health. Erik said that according to his research thus far, the best method for detection of his analyte would involve using a multiwave spectrophotometer, which has the ability to detect particle size and structure as well as wavelength absorption. This differs from mine in the fact that my method for detection will most likely include UV-Vis absorption detection through the usage of selective dyes. Also brevetoxin is a cyclic ether, and therefore much larger molecule than SLS and sodium octaneosulfate.
We both decided an issue that we would have to overcome would be interference from other compounds dissolved in the oceanic matrix that may interfere with our analytic technique of choice. Other compounds that are common in specific oceanic areas need to be investigated and categorized by standards or filters to discriminate them from our analyte in question.
1) Suitable methods for separation of DOSS would include GC , reverse phase , HILIC , and ion exchange chromatography . I would not consider size exclusion much use, because DOSS is not a large scale macromolecule, or would be separated from such in the matrix. Also, affinity chromatography would not be that applicable as retention factors that can be used in biological systems with proteins and the like would not find use with DOSS or other anionic surfactants. Finally chiral chromatography for an alkyl sulfate anionic surfactant doesn't serve much purpose, because the molecules chirality would not be nearly as detectable as other forms of separation.
2) After skimming through a couple of papers that use the techniques above for the identification and separation of surfactant compounds from water sources, the most logical and straight forward method for separation involves reverse phase chromatography. This method is simple enough that, after sample cleanup, standards can be used to compare the presence of DOSS in a sample, in the low ppb range.
3) A commercial column that would be suitable for this application is the LiChrospher 100 RP-18 according to Petrovic M. and Barcelo D. This can be purchased from Merck (cat # 1.50983.0001), has a particle size of 5um, length of 250mm and i.d. of 4mm. It has a pH range of 2-7.5 and is packed with particles of silica and octadecyl derivatives. ,
4) The mobile phase that would be utilized for this column would be varying mixtures of acetonitrile/water (80:20) or methanol/acetonitrile (50:50)
5) Although they in the literature for this specific study by Petrovic M. they stated that they utilized an atmospheric pressure chemical ionization (ACPI) mass spec with scanning ranges of (100-800 m/z) and injection mode (ESI).This is because their study focused on detecting a range of surfactants, being both amphoteric, nonionic, and ionic in nature.
Further research into chemical ionization methods found that a Quadrupole Mass Spec set to a negative chemical ionization (NCI) would be the best bet... since DOSS is a stable negative ion by itself. It is also been seen through multiple papers in the literature that those choosing to use a NCI Quad were often focusing on environmental detection issues.
(1) Antonio, D. C. Characterization of surfactants and their biointermediates by liquid chromatography-mass spectrometry. Journal of Chromatography A 1998, 794, 165-185.
(2) Boiani, J. Spectator ion indirect photometric detection of aliphatic anionic surfactants separated by reverse-phase high-performance liquid chromatography. Anal. Chem. 1987, 59, 2583.
(3) Bruins, A. P.; Drenth, B. F. H. Experiments With The Combination Of A Micro Liquid Chromatograph And A Chemical Ionization Quadrupole Mass Spectrometer, Using A Capillary Interface For Direct Liquid Introduction : Some theoretical considerations concerning the evaporation of liquids from capillaries into vacuum. Journal of Chromatography A 1983, 271, 71-82.
(4) de Hoffmann, E. In Mass spectrometry : principles and applications /; pp 14.
(5) Ding, W. -.; Ding, W. Determination of linear alkylbenzenesulfonates in sediments using pressurized liquid extraction and ion-pair derivatization gas chromatography-mass spectrometry. Anal. Chim. Acta 2000, 408, 291.
(6) Furton, K. G. Determining the critical micelle concentration of aqueous surfactant solutions: Using a novel colorimetric method. Journal of chemical education 1993, 70, 254.
(7) Guo, P.; Guo, P. Determination of linear alkylbenzene sulfonates by ion-pair solid-phase extraction and high-performance liquid chromatography. Talanta 2011, 84, 587.
(8) Petrovic, M. Determination of anionic and nonionic surfactants, their degradation products, and endocrine-disrupting compounds in sewage sludge by liquid chromatography/mass spectrometry. Anal. Chem. 2000, 72, 4560.
(9) Poppe, A. Negative-ion mass spectrometry. X. A spurious [CH5]- ion: problems with negative chemical-ionization quadrupole instrument. Org. Mass Spectrom. 1986, 21, 59.
(10) Rivera-Rodríguez, L. B.; Rodríguez-Estrella, R.; Ellington, J. J.; Evans, J. J. Quantification of low levels of organochlorine pesticides using small volumes (≤100 μl) of plasma of wild birds through gas chromatography negative chemical ionization mass spectrometry. Environmental Pollution 2007, 148, 654-662.
(11) Wu, S. H.; Pendleton, P. Adsorption of Anionic Surfactant by Activated Carbon: Effect of Surface Chemistry, Ionic Strength, and Hydrophobicity. J. Colloid Interface Sci. 2001, 243, 306-315.
(12) Yokoyama, Y. Determination of alkylbenzenesulphonates in environmental water by anion-exchange chromatography. J. Chromatogr. 1993, 643, 169.
(13) LiChrospher® 100 RP-18 and RP-18 Endcapped | Merck Chemicals International http://www.merck-chemicals.com/lichrospher-100-rp-18-and-rp-18-endcapped/c_DMOb.s1LSAoAAAEWsOAfVhTl (accessed 11/10/2011)
1) The CZE method along with the MEKC method would work for the detection of anionic surfactants.
2) The best method would most likely be the CZE method. This should help separate out the other compounds that are found it he matrix, and most importantly even separate other surfactants found in the dispersant by size and charge.
3) Conditions should be reversed to obtain positive peaks. Detections dime set at a constant of 0.5 s with a collection of 20 pts per second. A fused silica capillary with an i.d of 50um and lenthg of 75 cm (50 cm from point of injection). pH of 6-7 with methanol as the solution. To separate out different types of anionic surfactants, buffer of napthalenemonosulfonate or p-toluenesulfoate can be mixed 50:50 with methanol. 
4) While the paper states using an IDP detection with inversed detection of other ionic compounds in solution. I think that using an ESI to a mass spec would work just fine, and therefore would not have to deal with UV detection, since surfactants do not exhibit any fluorescence without dye conjugation.
 Shamsi S., Danielson N. Individual and Simultaneous Class Separations of Cationic and Anionic Surfactants Using Capillary Electrophoresis with Indirect Photometric Detection. Analytical Chemistry 1995 67 (22), 4210-4216
Cadmium (Cd) is an element that is a shiny, grey metal at room temperature(3). This toxic element is used in batteries, electroplating, and is a by-product of a few smelting processes at industrial plants. Long exposure or overexposure to Cadmium can result in cancer or severe damage to the kidneys, liver, and/or lungs. In 2003, it was determined that 0.001mg of Cd/kg of body weight was an acceptable daily intake for a person(2). As of 2005, the permissible exposure limit of Cd is 0.05mg/m^3(4). A study done in Sweden, in 2006, found an increase in Cadmium levels in people who ate local food grown near a battery factory(5).
I would like to do a comparative analysis of Cd levels within the blood of people living within a specific range of an industrial plant where Cd is used or a by-product. I hypothesize that people who live closer to the plant will have higher levels of Cd in their blood, but not necessarily high enough to cause severe organ damage.
UV-Vis absorption spectrometry
I do not believe that Cadmium itself absorbs in the UV-Vis range. To make UV-Vis relevant to determining the amount of Cd within blood, the Cd would need to be oxidized or react with a molecule to show up in the UV-Vis spectrum. To accomplish this task an oxidizing agent would have to be added, the resulting product separated as best can be, and then run through the machine.
The search, via Google, for info on Cadmium and UV-Vis absorption spectrometry turned up results of many compounds that included Cd and Cd lights, but none were of the UV-Vis absorption of pure Cadmium. The experiment is based off of numerous examples of compounds with oxidized Cd that turned up in the search results.
Similar Analytical Problems
(a) Andrew X. is studying Nitric oxide(NO) and muscle growth. His hypothesis is that NO does not promote muscle growth. His analyte is nitrate & nitrite, his matrix is blood, and the relevance of his topic is health and Research & Development of supplements.
Andrew S. is studying perfluorooctanoic acid(PFOA) levels in human blood. His hypothesis is that people living closer to plants using PFOA will have higher levels of PFOA in their blood than people living further away. His analyte is PFOA, his matrix is blood, and the relevance of his topic includes health, environment, and industrial.
(b) All three of our studies include a blood matrix and working on being able to clearly determine the analyte from the matrix with whatever techniques we use. All of our topics are also related to health in some manner. Andrew S. and I plan to sample blood at various ranges from industrial plants utilizing our analytes. Andrew Z. and I may both have to look at a modified analyte compound to use an analytical technique learned in the course, if the analytes do not have the properties needed for the learned techniques. All three studies will include sample comparisons of the analytes in order to determine the validity of the hypotheses and to accurately report the results.
(c) Andrew Z. will have a different factor in determining who to sample for analyte comparison, as his analyte is not related to industrial usage. My analyte is an elemental metal, while the Andrews analytes are compounds with organic properties that may increase the difficulty in separation from the blood matrix.
Studies for Investigation
Hypothesis: Cadmium levels in the blood will be higher in people living within 100 miles of a plant, that uses or has Cd as a by-product, than people living between 200 to 300 miles of the same plant.
Studies: (A) Identifying locations of people within the specific ranges of the chosen plant(s). (B) Determination of need and location for control group of Cd levels within blood. (C) Measure Cd levels in the blood from interested areas.
Alternative Studies: (D) If Cadmium levels are the same or indeterminable in all tests, investigate the possibility of other compounds being formed that would effect the levels.
>>>Note: Levels of Cadmium being studied will most likely be in µg/mL of blood (6).
Cadmium itself does not have fluorescent properties. Using 2-(o-hydroxyphenyl)-benzoxazole, as a reagent to derivatize Cadmium, an absorbance at 365nm is obtained and a blue fluorescent emission is observed (6). A fluorometer would be useful in obtaining emission data, since most or all interference from the source would be removed. A fiber-optic fluorescence sensor would also be useful for gathering emission data. A spectrofluorometer would be useful in getting the absorption and emission data, which could be helpful in determining possible interference from the blood matrix (6).
Chemical Structure and Standards
Common species present in matrix: Cd(II)O, Cd(II)Cl2, and Cd(II)S (7).
Standards can be made and used from Sigma Aldrich (9).
Compound -- Catalogue # ----- Quantitiy ------ Price
CdO ---------- 202894-5G ------ 5 grams ------ $33.40
----------------- 202894-25G ---- 25 grams ----- $107.00
CdS ---------- 217921-20G ----- 20 grams ----- $64.30
CdCl2 -------- 439800-5G ------- 5 grams ------ $68.30
----------------- 439800-25G ----- 25 grams ----- $241.50
----------------- 02786-1EA ------- 1 Liter --------- $20.70 ----- (1g CdCl2/1L water)
Atomic and Mass Spectrometries
Atomic Absorption Spectroscopy (AAS) can be used.
The analyte Cadmium has an absorption wavelength at 228.8nm(10).
Electrothermal vaporization would be used to allow the straight injection of the blood sample without diluting the sample(6).
>>Mass Spectrometry (6)
Cadmium - 112.411 g/mol
Inductively Coupled Plasma-Quadrupole (ICP-Quad)
Sample Preparation Procedures(11)
(1) Digestion: add acids to blood sample (10-100mL of blood).
(2) Evaporation: evaporate the solution down to 15-20mL.
(3) Acidify and Evap.: add Sulfuric Acid and evaporate until solution becomes clear from evaporation of SO3.
(4) Dilution: cool solution and dilute with 50mL of PDCA (pyridine-2,6-dicarboxylic acid) eluent.
1: Ion-exchange, Size-exclusion, and Affinity chromatography would be useful. Chiral chromatography would not be useful because none of the analytes are chiral. Gas-chromatography would not be useful because the boiling points of Cadmium and the Cadmium compounds are greater than 350 °C (9).
2: Ion-exchange chromatography would be my first choice because the Cadmium (II) ion is a common species found in the blood matrix (7).
3: IonPac CS5A Transition Metal Column. Dionex Corp. Catalogue # 052576 (12)
>>>4 x 250mm or 2 x 250mm; Bead diameter = 9µm; Latex diameter = 140nm;
max pressure of 2500psi; ion-exchange group = sulfonic acid
4: PDCA for the mobile phase (11).
5: Absorbance detector because it can get a reading at the 10pg level (6). MS could work, but larger aromatic compounds could interfere with the analysis.
Capillary Electrophoresis Techniques
1: Capillary Zone electrophoresis (CZE), Micellar electrokinetic chromatography (MEKC), and Capillary gel electrophoresis (CGE) have potential use for analysis. Capillary isoelectric focusing (cIEF) might not be a good technique with numerous compounds in the matrix being stable at a similar pH.
2: I would use CZE, since information from prior experiments using the technique for Cadmium analysis can be used to narrow the possible experimental procedures needed.
3: Fused-silica capillaries, 75 µm I.D., and 52 cm from point of sample introduction to detector. 10 cm hydrostatic injection of sample. Indirect UV detection at 214 nm for 30s by zinc lamp. pH = 4.4, voltage = 20kV, 6.5 mM α-hydroxyisobutyric acid (HIBA) as a carrier electrolyte. (13)
4: Indirect UV-Vis Absorption. It has been used before and can detect ppb of analyte. (13, 14)
Cadmium is electroactive. Potentiometric stripping analysis (PSA) using a mercury film electrode would be used to identify the analyte. A reference curve of sample would be made to determine the quantity of analyte. (15)
(1) Environmental Protection Agency. Technology Transfer Network: Air Toxics Web Site. http://www.epa.gov/ttnatw01/hlthef/cadmium.html#ref1 (Accessed Sept 19, 2011).
(2) NSF International. NSF International Web Site. http://www.nsf.org/business/newsroom/pdf/DS_Metal_Contaminant_Acceptance_Levels.pdf (Accessed Sept. 29, 2011).
(3) Science Lab: Chemicals & Laboratory Equipment. ScienceLab.com Web Site. http://www.sciencelab.com/msds.php?msdsId=9923223 (Accessed Sept. 29, 2011).
(4) The Physical and Theoretical Chemistry Laboratory Oxford University. Chemical and Other Safety Information. http://msds.chem.ox.ac.uk/CA/cadmium (Accessed Sept. 29, 2011).
(5) Science Direct.Scientific Database. http://www.sciencedirect.com/science/article/pii/S0048969706008941 (Accessed Sept. 29, 2011).
(6) Crouch, Stanley R.; Holler, F. James; Skoog, Douglas A. Principles of Insrumental Analysis, 6th ed.; Brooks/Cole: Belmont, CA, 2007.
(7) Environmental Bureau of Investigation. Contaminants: Cadmium. http://www.eprf.ca/ebi/contaminants/cadmium.html (accessed Oct 25, 2011).
(8) WebElements. Chemistry: Periodic Table: Cadmium: Compounds Information. http://www.webelements.com/cadmium/compounds.html (accessed Oct 25, 2011).
(9) Sigma-Aldrich. http://www.sigmaaldrich.com/united-states.html (accessed Oct 25, 2011).
(10) Energy Research Centre of the Netherlands. http://www.ecn.nl/docs/society/horizontal/hor20_AAS.pdf (accessed Oct 27, 2011).
(11) Dionex Corp. Determination of Transition Metals in Serum and Whole Blood by Ion Chromatography. http://www.dionex.com/en-us/webdocs/4201-AN108_V12.pdf (accessed Nov 3, 2011).
(12) Dionex Crop. Products: IonPac CS5A Transition Metal Column. http://www.dionex.com/en-us/products/columns/ic-rfic/transition-metal-packed/ionpac-cs5a/lp-73276.html (accessed 11/10/11).
(13) Weston, Andrea; Brown, Phyllis R.; Jandik, Pter; Jones, william R.; Heckenberg, Allan L. Factors affecting the separation of inorganic metal cations by capillary electrophoresis. Journal of Chromatography 1992, 593, 289-295.
(14) Francois, C.; Morin, Ph.; Dreux, M. Separation of transition metal cations by capillary electrophoresis Optimization of complexing agent concentrations (lactic acid and 18-crown-6). Journal of Chromatography 1995, 717, 393-408.
(15) Ostapczuk, P. Present potentials and limitations in the determination of trace elements by potentiometric stripping analysis. Analytica Chimica Acta1993, 273, 35-40.
There are many antimicrobial agents found in soaps. One of the most widely used is Triclocarban (TCC,3,4,4'-trichlorocarbanilide). Toxicological studies in the 1970s concluded that TCC was safe to use in personal care products but recent findings reveal significant biological effects. Studies show that at high concentrations, TCC may act as an agonist to testosterone and other steroids which are also known as endocrine disrupting substances (EDS). Because of its widespread use, studies revealed the presence of TCC in surface water in large concentrations (g/L) and in other biological organisms such as algae and snails. Moreover, US EPA reports detected TCC in all 84 sewage samples with concentrations as high as 0.44 g/kg. These studies reveal the high persistency of TCC in the environment, which may be likely due to the use of antimicrobial soaps and detergents by humans.
While studies have shown the presence the TCC in the environment, the proposed analytical problem would be to detect TCC in human serum, mainly urine samples. This is important since exposure to TCC could influence human health. Animal studies have shown that EDS and such chemicals linked to a variety of problems including cancer, reproductive failure and developmental anomalies. These problems may translate into the human biological system and the FDA has begun its investigation. The hypothesis is that with continued exposure to TCC through daily activities such as showering and washing hands that TCC enters the human biological system. By analyzing urine samples, human exposure to TCC will be monitored and determined.
1. Schebb, N. H.; Inceoglu, B.; Ahn, K. C.; Morisseau, C.; Gee, S. J.; Hammock, B. D. Investigation of Human Exposure to Triclocarban after Showering and Preliminary Evaluation of its Biological Effects. Environ. Sci. Technol. 2011, 45, 3109-3115.
2. ScienceDaily. Antibacterial Chemical Disrupts Hormone Activities, Study Finds. http://www.sciencedaily.com /releases/2007/12/071207150713.htm (accessed September 19, 2011).
UV-Vis Absorption Spectrometry
Jungerman and Beck determined germicide mixtures in soaps and detergents by preparing acidic and basic alcohol mixtures of TCC to be analyzed by UV-Vis spectrophotometry. The acidic alcohol sample was prepared with 95% ethanol (96mL) with glacial acetic acid (4mL) while the basic alcohol sample was prepared with 95% ethanol (96mL) and concentrated ammonium hydroxide (4mL). These samples were then analyzed for absorbance between 220 nm and 400 nm. The spectrum revealed that TCC absorbed the most between 200 and 280 nm with the two highest points of absorbance at about 210 nm and 265 nm. An extinction maxima was determined to be 265 nm for both the acidic and basic samples.
The researchers also used the same methods to detect other trichloro compounds that are also used as bacteriostatic additives to soaps of which have very similar organic structure to TCC. Their experiments revealed that these trichloro compounds do absorb the highest at wavelengths of about 260 to 300 nm. Therefore if a more modern experimental procedure were to be performed, the same solvent mixture would be used and the wavelength range above would be used to analyze the presence of TCC in urine samples. Of course these urine samples must first be purified and TCC extracted to a pure sample in order to reduce noise and other contaminant signals. I have yet to research and find an appropriate method to the purification of TCC.
3. Jungerman, E.; Beck, E.C. Determination of Germicide Mixtures in Soaps and Detergents. Journal of the American Oil Chemist's Society. 1961, 38, 513-515
Similar Analytical Problem: My analytical problem is similar to John Raia's Detection of Analytical Surfactants in Water since my compound is also used in large scales and are manufactured in different soaps and detergent products. For a more in depth explanation, please view John Raia's blog postings.
Similar Analytical Problem(s)
One similar analytical problem is Rajva Mehta's dealing with DEHP leaching from PVC into contents of medical devices. Our analytes include chlorine compounds that may cause human biological effects and are considered carcinogens. She will be testing blood and plasma samples and will have to follow multiple purification steps such as in my analytical problem to isolate the desired analyte. Her hypothesis is that with continued exposure to DEHP, many more adverse health effects could manifest and be detrimental to the human body. Another similar problem is Perfluorooctanoic acid levels in human blood by Andrew Szeliga. While his analyte contains Fluorine, our problems are similar that our compounds contain halogens and would need to test human bodily fluid tests. He hypothesizes that people living or working in close proximity to sources of PFOA will have dangerously elevated levels of PFOA in their bloodstream. The studies that we both will have to conduct is to compare samples against a control. These experiments will allow us to conclude the presence of our analytes in the human body.
Hypothesis: Continued exposure to TCC through daily activities such as showering and washing hands with soaps and detergents containing the antimicrobial will cause TCC to enter into the human biological system.
Studies: (1) Get a representative sample group of people for the study (i.e. those who live in the cities, suburbs, and rural areas) because the use of soaps may depend on the location of individuals. (2) Divide the group into two main focus areas: Shower study (focus on TCC and personal hygiene) and Dish study (focus on TCC and ingestion by utensils, etc.). The shower study will be given shampoo/body wash containing TCC and given dish washing soap without TCC and vice versa for the dish study. (3) Create a detailed plan entitling each individual a set time of the day to either shower/wash dishes with TCC containing soaps/detergents (each individual will follow these same instructions) (4) Prior to beginning the experiment, the participants will be given shampoo/body wash and dish washing detergent not containing TCC as to set a sample standard and measure the levels of TCC as the experiment progresses. (5) Start the experiment - Group 1: control (non TCC Dish and Shower), Group 2: Dish Study (TCC dish washing detergent and non TCC shampoo), Group 3: Shower Study (TCC shampoo and non TCC dish washing detergent), Group 4: Dish and Shower (both contains TCC) (6) Measure levels of TCC accumulation in the human biological system by collecting urine samples weekly in each individual of every group.
Alternative Studies: After collecting data for a month, the experiment can eventually be extended to three months. After those three months of TCC accumulation, we can set up a study to observe how fast the rate of disappearance of TCC will be in each case study and individual. This will be done by the same process and methods by collecting urine samples and measuring the levels of TCC present.
Chemical Structure and Standards
Cambridge Isotope Laboratories, Inc.
Description: Isotopically labeled Triclocarban (4'-CHLOROPHENYL-13C6, 99%), 100 ug/mL in CH3CN
Catalog Number: CLM-7286-1.2
Quantity: 1.2 mL
http://www.isotope.com/cil/products/displayproduct.cfm?prod_id=9241 (Date Accessed Oct. 25, 2011)
Atomic and Mass Spectrometries
Atomic spectrometry cannot be used to quantify Triclocarban. However, two types of mass spectrometry, ESI-Quad and ESI-linear trap-FT-ICR, can be used to quantify Triclocarban (MW = 315.58 g/mol). Electrospray ionization will be used as the ionization source and triple quadrupole and an ion trap as the mass analyzers. In the research article I found, the conditions used to obtain the mass spectrum were the flow injection of 10 ng of analyte with the scanning in the m/z range of 275-400. In order to detect the base ion and its acetic acid adduct ion, an eluent mixture containing acetonitrile (70%), water (30%), and acetic acid (10mM) was used because the method was LC MS with liquid chromatography preceding the injection of analyte into the mass spectrum. This is to purify sample from other possible contaminants. The analyte mass spectrum was compared to an internal standard mass spectrum of radiolabeled Triclocarban (13C6).
Halden, R. U.; Paull, D. H.; Analysis of Triclocarban in Aquatic Samples by Liquid Chromatography Electrospray Ionization Mass Spectrometry. Environ. Sci. Technol. 2004, 38, 4849-4855
Sample Preparation Procedures
Direct Urine Analysis
(1) Centrifugation: 50-100 uL aliquots of urine will be mixed with an internal standard (IS) solution 1/1 (v/v), vortexed, followed by centrifugation (16,000 g) at 4 C for 5 min.
(2) Anaylsis: The supernatant will be directly injected into an LCMS.
Urine Analysis after Hydrolysis
(1) HCl (100 uL) will be added to 500 uL of sample urine to produce a final acid concentration of 1 M in a 3 mL glass vial.
(2) The mixtures are vortexed and heated (20 min) to 100 C, cooled down on ice, and will be neutralized with 6 M aq NaOH (90 uL)
(3) An aliquot of resulting solution will be mixed with IS solution 1:4 (v/v) and analyzed by LCMS.Source: View Source 1 above
From different research articles and from class lectures, reverse phased HPLC would be most suitable to separate my analyte from other matrix components because my analyte TCC is polar and would elute readily as compared to other techniques. My compound is not chiral and therefore chiral chromatography is not suitable and size exclusion has too low of a resolution for my analysis. Gas chromatography might not be ideal since my compound is known not to be that volatile. However, ion exchange chromatography may also be suitable since it separates compounds based off polarity and my analyte is quite polar. My first choice would be reversed phase HPLC because it suits ideally to separate my polar compound from a possible compound in similarity, Triclosan, from the mixture and is much faster as well as more cost efficient if I were to perform the experiment on a large scale.
A suitable commercial column can be purchased from Waters (Product Number: 176000863): ACQUITY UPLC BEH C18 Column, 2.1 x 50 mm, 1.7 µm, 3/pk. The trifunctionally bonded BEH particle gives a very wide usable pH range (pH 1-12), superior low pH stability, and ultra-low column bleed for high sensitivity MS applications.
The mobile phase will consist of a buffer solution (A) and run on a gradient with acetonitrile (B) as follows by Guo et. al.:0 min, 50% A/50% B with a flow rate of 0.4mLmin−1, then 40% A/60% B with a flow rate of 0.5mLmin−1 at 1.0min, finally, reconditioning the column with 50% A/50% B after washing column with 90% B at the rate of 0.3mLmin−1 for 1.5 min.
I would use a MS detector because it is most sensitive to detect trace levels of my analyte mixture (up to pico grams).
http://www.waters.com/waters/partDetail.htm?partNumber=176000863 (Date Accessed: Nov 10, 2011)
(source will follow this blog posting)
Capillary Electrophoresis Techniques
Capillary Zone Electrophoresis (CZE) and Micellar Electrokinetic Chromatography (MEKC) are the two types of capillary electrophoresis that would be suitable to separate my analyte. CZE would work best because TCC may exist as an anionic species and with an applied voltage, the ionic analyte may be separated due to its size and charge from other contaminants especially Triclosan (TCS) that has a similar charge but is smaller in size and therefore would help to detect TCC more easily. MEKC would be suitable since TCC is hydrophobic in nature and would therefore distribute itself between the hydrophobic interior of the micelles and the hydrophilic exterior buffer solution. Capillary Gel Electrophoresis (CGE) and cIEF would not be suitable because they both are usually performed to separate proteins or biological molecules.
My first choice would be CZE because it will allow for an efficient separation of my charged analyte mixture and does not require a micellar mixture which may impact cost efficiency if this were to be performed on a large scale. It is also the preferred technique to separate small ions such as TCC.
Since TCC is expected to exist as an anionic mixture, a coated capillary tube is ideal. My buffer would be acetonitrile at a basic pH (~8-9) in order to separate my anionic species.
I would perform this separation in tandem with a mass spectrometer because it would be able to detect minute concentrations of my analyte. A MS detector is also chosen because it is one of the few techniques that is suitable for detection of my analyte TCC because other analytical techniques do not work such as AES and Fluorescence Spectroscopy. It has a very low limit of detection at 1-0.01 attomoles as compared to other techniques and is suitable for my hypothesis because it will allow for an accurate detection of TCC in urine.
Triclocarban is electroactive because it contains a carbonyl group that bridges the two chlorinated benzene rings. However, TCC has an extremely low water solubility (<2 mgL-1) which prevents the study of its electrochemical degradation in an aqueous medium. As noted in Sires et. al.Triclocarban, including a possible contaminant in my analytical project, Triclosan, both of which are antimicrobial agents, can be oxidized to give stable intermediates by Electro-Fenton degradation. The main oxidant as described in this system is the hydroxyl radical that is produced on both the anode surface and from water oxidation and in the medium by Fenton's Reaction. This reaction takes place between electrogenerated H2O2 and Fe2+ coming from the cathodic reduction of O2 and Fe3+.
TCC can produce four stable intermediates: two hydroxylated derivatives (hydroquinone and chlorohydroquinone) and two nitroderivatives (1-chloro-4-nitrobenzene and 1,2-dichloro-4-nitrobenzene).
In order to identify TCC using electrochemistry, a Pt/O2 diffusion cell will be used and samples of TCC (standards at different known molar concentrations as well as the patient urine samples) will be prepared with 0.05M Na2SO4 as the background electrolyte and 0.20mM Fe3+ as catalyst at pH 3.0. The electro-Fenton system will be operated at 60 mA and at room temperature.
The samples will be added to a solution of acetonitrile/water (v/v) and subject to electrolysis (~10 min) where the mixture will be analyzed by GC/MS to identify the hydroxylated derivatives and the nitroderivatives. Sires et. al. provided a table of the retention times as well as the molecular peak of the intermediates which may be used in comparison for the identification of TCC in my analytical problem if this technique were to be used.
In order to quantify my unknown concentration of TCC in human urine, I first will have to make a standard plot of the concentration of TCC versus time in known molar amounts in different acetonitrile/water (v/v) systems. After the decay of TCC by electrolysis, reversed-phase HPLC will follow in order to quantify the amount of generated carboxylic acids from the degradation by ion-exclusion chromatography. This amount will be a direct correlation to the amount of TCC in the solution and therefore a standard plot can be produced. Unknown samples will be subject to degradation and LC will provide quantitative results of generated carboxylic acids which is then compared to these standard curves for quantitation.
Source: Sires, I.; Oturan, N.; Oturan, M. A.; Rodriguez, R. M.; Garrido, J. A.; Brillas, E. Electro-Fenton Degradation of Antimicrobials Triclosan and Triclocarban. Electrochimica Acta. 2007, 52, 5493-5503
My analytical problem is that develop a safe way (can't cheatable) to find out the concentration of aflatoxin in the vegetarian oil.
I want to do such an analytical problem because aflatoxin contamination is serious in China. Most cases of such contamination are found in the food oil in Chinese market. The small restaurant repeatly use the oil simple recycled from the sewer and the hood from the big restaurant. After several days transport and process, the oil touch too much fungi for a long time, the fatty acid is transferred to be aflatoxin. (1) Aflatoxin is a dangerous thing which can cause cancer. (1) Aflatoxin processed by liver and become a kind of oxide product which is the real poisonous stuff. (1)
The central hypothesis is that there's excess aflatoxin in the recycled oil which come from the old oil, and the excess aflatoxin makes people unhealthy. Of course, the analyte is aflatoxin. The aflatoxin come from a matrix of fatty acid/heavy metal (because one of the process of recycling)/food/water and some aromatic impurities.
1). Watanabe, Coran M.H.; Townsend, Craig A. Initial Characterization of a Type I Fatty Acid Synthase and Polyketide Synthase Multienzyme Complex NorS in the Biosynthesis of Aflatoxin B. Chemistry & Biology; Sep2002, Vol. 9 Issue 9, p981, 8p.
UV-Vis absorption spectrometry
The aflatoxins in the food are four type B1/B2/G1/G2. However, they're almost the same structures, so they have the same maximum absorption wavelength. The other types of aflatoxins are ignored because they arent common exsits in decaied food oil.
In methanol, 265nm and 360-362nm wavelength
B1 12400e 21800e
B2 12100e 24000e
G1 9600e 17700e
G2 8200e 17100e
Fact sheet of aflatoxin. http://www.micotoxinas.com.br/aflafacts.pdf (accessed Sept 2011).
Similar Analytical Problem(s)
Pesticides and Toxins in fragrances and natural flavors
Topic: presence of residual pesticides, or natural toxins in natural flavors and fragrances
Hypothesis: these toxins and pesticides are concentrated in the raw materials for naturally flavors and fragrances
Analytes: common pesticides, naturally produced plant toxins, heavy metals
Matrixes: alcohol, powdered, in oil emulsions, and occasionally in water
Simialr: we all focus on the things that come from a natural resource. So, the studies base on the toxins are produced with a process independent way (the toxins are not produced by the process/the tools of the process or the environment of the factory). A studies about the environment and planting method of the natrual raw material of the products is also needed to prove that the toxins come/not come from the natral raw material (flowers/beans etc.). The studies on other toxins exsitence in the product should also included in the research (so the problems caused by these toxins). A studies of customer method for using the product is another important studies. The same condition lab/sample comparison studeis should also me performed.
Different: he need to studies on eliminate the effect of the natrual flavor matrix on the signal while I will do the studeis on the interference of the food oil matrix on the signal.
Topic: proteins and Fruit Allergies
Hypothesis: any minor genetic altering of a plant will not affect the proteins that cause the allergic reactions
Analytes: minor genetic altering of a plant's protein won't cause diease
Matrix: juice would also contain carbohydrates and other organic molecules
Similar: we all focus on the things that come from a natural resource. So, the studies base on the toxins are produced with a process independent way (the toxins are not produced by the process/the tools of the process or the environment of the factory). A studies about the environment and planting method of the natrual raw material of the products is also needed to prove that the toxins come/not come from the natral raw material. The studies on other toxins exsitence in the product should also included in the research. A studies of customer method for using the product is another important studies.The same condition lab/sample comparison studeis should also me performed.
Different: he need to studeis on all the types minor genetic modification of the fruites don affect the proteins levels, and secure the signal from the fruite matrix. I need to make sure the signal is OK from the matrix of the food oil.
Properties of aflatoxin and it producing fungi. http://www.icrisat.org/aflatoxin/aflatoxin.asp (accessed October 2011).
Sigma-Aldrich company's Aflatoxin B1/B2/G1/G2 Standard Solution (46323-U 46324-U 46325-U 46326-U) will be used.
For now, I will need two sets (4 solutions * 2) of the solutions, one is for atomic spectra, and the other one is for the mass spectra, if I will use the light based instrument (probably wont use because they are not accurate as I expected), there are will be another set of the soultions.
Each solution is 0.5 μg/mL (1 mL per pkg) in acetonitrile with a price of 43 USD.
The aflatoxin has electronactive property.
For identify, they have half potential near 1.2V. (chapter 3.22)
For quantify, there's calibration curve for them. (chapter 188.8.131.52)
http://eprints.utm.my/2889/1/75152.pdf (2011 DEC acessed).
Arsenic concentrations in ground water in many west-central Minnesotan wells are currently above the U.S. federal drinking water standard of 10 μg/L. This is a naturally occurring phenomenon that has been associated with the glaciated regions in the upper Midwest. In order to re-mediate these high concentrations to comply with the public health standards a better understanding of the mechanisms that cause arsenic release from solids and into ground water are needed.
Arsenic exposure from contaminated drinking water is a significant environmental cancer risk, equivalent to environmental tobacco smoke and home radon exposure. With an approximate 150,000 to 250,000 Minnesotans getting their drinking water from contaminated wells, the public health standards need to be met.
The general hypothesis is that there are certain hydrogeochemical conditions prevalent in glaciated regions that make arsenic more mobile. Primarily, that the presence of certain arsenic species that are more mobile in the particular hydrogeochemical conditions of the region result in the higher concentrations of arsenic in the ground water.
The analyte is Arsenic in its varying forms across the species that exist in the soil. Arsenic exists in a few hundred common minerals. For example, in reducing environments arsenic is present in iron sulfides such as arsenopyrite (FeAsS), realgar (AsS), and orpiment (A2S3). It can also be found as a contaminant in pyrite (FeS). In oxidizing environments, arsenic is found in arsenic trioxides (arsenolite: As2O3 and claudetite: As2O3). Under a wider range of geological conditions, arsenic has also been associated with minerals such as iron oxides (Fe2O3), iron hydroxides (FeOOH), and other metal oxides and hydroxides (such as Al). In natural fresh waters, arsenic, if present, is generally an inorganic species. In reduced environments, the form of Arsenite (As(III) as H3AsO3 and its dissociation constituents) is predominate . Arsenate (As(V) a H3AsO4 and its dissociation constituents) predominates in oxic environments.
Berg, J. A., 2008. Hydrogeology of the Surficial and Buried Aquifers Regional Hydrogeological Assessment, RHA- 6, part B, Plates 1-6. State of Minnesota, Department of Natural Resources, Division of Waters.
Erickson, Melinda L., and Randal J. Barnes. "Glacial Sediment Causing Regional-Scale Elevated Arsenic in Drinking Water." Ground Water 43(2005a): 796-805.
Similar Analytical Problem
a. Boron in MN Groundwater, Justin Michael is trying to determine what is the most effective and cost-efficient way to remediate Boron contamination. Boric Acid and Boron Anions are the analyte and the matrix they are found in is the Groundwater. This is a health concern.
b. We will both need to take a wide variety of samples to get an idea of how the system is working and responding. We will both need to test water samples.
c. Justin is concerned with cleaning up the Boron where I am more interested in finding our where the Arsenic is coming from so Justin will treat his samples in lab to determine the effectiveness of a technique then apply that technique in the environment and monitor its affect. I will basically be surveying soils and water samples to gather more information about how Arsenic is present in the soil to see if I can draw any conclusions.
1. Need to identify the different types of arsenic found in the soil. Use multiple soil sources both near contaminated wells and near clean wells. In addition to analyzing various locations also analyzing different depths.
2. Quantify how much arsenic exists in each state in each soil sample.
3. Take into account other environmental conditions such as reducing environments and water pH.
4. Using GIS modeling input all factors and see if trends exist and if we can come to any conclusions.
I expect contaminate levels in the ppm
I found a very useful paper describing arsenic measurements using Atomic Fluorescent Spectroscopy (AFS). According to their study the strongest emission signal was obtained at a wavelength of 2350 angstroms (235 nm) with a corresponding absorption signal at 1890 angstroms (189 nm) . One thing to note is that at concentrations above 200 ppm the calibration curves begin to curve dramatically. This is because when there is a larger density of As atoms causes self-absorption of the emitted resonance radiation.
Signal strength seems to be greatly impacted by the excitation source and a hydride generation technique seems to work best for low concentrations.
Chemical Structure and Standards
Structures for Realgar, Tetraarsenic Oxide, and Arsenic Trioxide:
Structure of Arsenopyrite:
o2si offers Arsenic standards for making a calibration curve but I also think it would be a good idea to test our entire method by sorbing arsenic in known concentrations onto geothite or another mineral. An example of a procedure was found in the following paper:
Yes we can use atomic spectrometry to detect arsenic. Perkin Elmer recommends using 193.7 nm for the wavelength. A Flow Injection Analysis System (FIAS) - Atomic Absorption Spectrophotometer is hydride generation technique that is commonly used for quantifying arsenic. Using a hydride generation technique is a important to separate hydride forming metals, such as As, from a range of matrices and varying acid
concentrations. This analytical technique can improve detection limits by a factor of approximately 3000 times that of flame detection limits and typically have less interference than graphite furnace techniques. This is important when I am working with concentrations in ppb.
a. Arsenic(V): 74.92
c. quadrupole ion trap
1. If we had a high enough fraction of organic As compounds we could use GC, because these compounds tend to be very volatile, but I am predicting mainly inorganic As which would not benefit from GC. There is not enough difference in polarity of the inorganic As species for HILIC to be effective. Affinity Chromatography is mainly for biochemical mixtures. Most of the species I am looking at do not have chiral centers so Chiral Chromatography will be ineffective. One big separation we have to be able to accomplish is separating the different oxidation states (AsIII and AsV). Size Exclusion Chromatography is more designed for macromolecules so isn't able to accomplish what we need.
2. Ion exchange would be my first choice. Anion Exchange Chromatography (AEX) separates the common As species but Cation Exchange Chromatography (CEX) does not retain the two most toxic species (AsIII and AsV). In most cases AEX does a good enough job at separating all the species but sometimes using a mixed-mode anion-cation exchanger yields better results.
3. The Alltech Anion HC column (Part #: 269036 4.6 x 100 mm) reported good results for this analysis. It is packed with a polystyrene divinylbenzene-based anion-exchanger, having a quaternary amine functional group. It is capable of operating over a pH of 2-12, which is essential since most As compounds are only stable at pH < 3 and pH > 9. Particle size of 12 microns with a capacity of 3 meq/g. No information on back-pressure was reported but this particle size is withing normal operating sizes of many columns so back-pressure should not be too much of an issue to overcome.
4. Several concentrations of both ammonium dihydrogen phosphate and sodium hydroxide have been evaluated in both isocratic and gradient methods. A gradient elution involving 10mmol/L ammonium dihydrogen phosphate solution and water had the shortest analysis time with good resolution.
5. ICP MS is my choice of a detector because we are working with many different species in concentrations in the ppb and it is the most versatile and sensitive method.
7. Khalid H. Al-Assaf, Julian F. Tyson, & Peter C. Uden. (2009). Determination of four arsenic species in soil by sequential extraction and high performance liquid chromatography with post-column hydride generation and inductively coupled plasma optical emission spectrometry detectionThis article is part of a themed.. JAAS (Journal of Analytical Atomic Spectrometry), 24(4), 376-384. Retrieved from http://search.ebscohost.com/login.aspx?direct=true&db=aph&AN=37142308&site=ehost-live
Ricci, G. R., Shepard, L. S., Colovos, G., & Hester, N. E. (1981). Ion chromatography with atomic absorption spectrometric detection for determination of organic and inorganic arsenic species. Analytical Chemistry, 53(4), 610-613. doi:10.1021/ac00227a012
Kozak, L., Niedzielski, P., & Szczuciński, W. (2008). The methodology and results of determination of inorganic arsenic species in mobile fractions of tsunami deposits by a hyphenated technique of HPLC-HG-AAS. International Journal of Environmental Analytical Chemistry, 88(14), 989-1003. doi:10.1080/03067310802183852
Problems using similar techniques: Blog 10
2. Matthew Marah - AAS
1.CE has proven to be an excellent technique for separating the various Arsenic species found in the soil. The various oxidation states of the inorganic compounds and the differences in polarity of the organic species make separation ideal for CE. CZE is the most commonly used and the separation works great so while MEKC and CGE can be used it is rather unnecessary. In some cases using isoelectric focusing has improved results.
2.Using CZE will be the best method because an ideal separation can be achieved without any additional effort or techniques.
3. One buffer used for these analytes can be prepared by mixing 50 mM formic acid and 50 mM ammonium formate, adjusted to pH 2.9-5.0. Separations of samples could be accomplished by applying a 120 kV potential. One type of capillary found to be used is an untreated fused-silica capillary (50 mm id, 365 mm od, 40-70 cm total length) obtained from Polymicro Technologies, Phoenix, AZ, USA.
4.Because of the low concentrations in the samples UV detection is generally insufficient due to a short optical path length. As a result MS is the most favorable detector. ICP-MS is the most common but more recently ISI-MS has been getting looked into for this particular analytical problem.
Kitagawa, F., Shiomi, K. and Otsuka, K. (2006), Analysis of arsenic compounds by capillary electrophoresis using indirect UV and mass spectrometric detections. ELECTROPHORESIS, 27: 2233-2239. doi: 10.1002/elps.200500614
Large numbers of college students turn to energy drinks for a "quick boost," some infrequently and others almost every day. Most energy drinks contain large amounts of caffeine, plus other assorted organic compounds which claim to boost energy. One of these compounds is taurine, a sulfonic acid commonly classified as an amino acid. Taurine is typically ingested through meat, and is important for skeletal muscle growth and functioning. When added to energy drinks, marketers claim it boosts energy, increases concentration and memory and supplements physical performance. However, the quantities added are far below levels of taurine shown to produce such effects. Additionally, taurine and caffeine are known to have adverse interactions, although these have not been thoroughly studied or quantified. One of the major interactions appears to be increased cardiac stress in the form of increased stroke volume. Accurately determining the taurine content is these energy drinks is important, because people may be consuming levels of taurine that can interact with the caffeine in these drinks to cause cardiac stress.
The hypothesis is that taurine levels in energy drinks are less than the standard effective dosage for taurine, but great enough to cause harmful interactions with caffeine. Essentially, the taurine in energy drinks is not great enough to add any benefits, but prevalent enough to cause cardiac distress. The primary analyte is taurine, and the matrix is the energy drink, including the added caffeine, sugars, vitamins, and organic compounds.
Clauson, K.A.; Shields, K.M.; McQueen, C.E.; Persad, N. Safety issues associated with
commercially available energy drinks. J. Amer. Pharm. Assoc.[Online] 2008, 48, e55-e67. http://www.pharmacytoday.org/pdf/2008/May_CE_exam.pdf (accessed Sept 20, 2011).
Reissig, C.J.; Strain, E.C.; Griffiths, R.R. Caffeinated energy drinks--A growing problem. Drug Alcoh. Dep.[Online] 2009, 99, 1-10. http://www.sciencedirect.com.ezp1.lib.umn.edu/science/article/pii/S0376871608002858 (accessed Sept 20, 2011).
UV-Vis absorption spectrometry
Taurine does not have detectable uv-vis activity. However, numerous different compounds can be complexed with taurine to obtain either uv-vis or fluorescent spectra. One method that has shown success in complex matrices, such as energy drinks, is derivitization with 4-fluoro-7-nitrobenzofurazan (NBD-F). To create this complex, a small amount of energy drink is heated with EDTA and the NBD-F. After 10 minutes at 60 degrees Celsius, the complex is formed an can be analyzed at 470 nm.
To find information on uv-vis data for taurine, I performed a journal search for papers that determined taurine content and provided uv-vis data. This search lead me to numerous publications explaining different methods for complexing taurine.
Sawabe, Y.; Tagami, T.; Yamasaki, K. Determination of Taurine in Energy Drinks by HPLC Using a Pre-Column Derivative. J. Health Sci.[Online] 2008, 54, 661-664. http://jhs.pharm.or.jp/data/54%286%29/54_661.pdf (accessed Sept 29, 2011).
See "Andrew-Xayamongkhon-Analytical Problem- Nitric oxide and muscle growth" for similarities between our problems.
Similar Analytical Problem(s)
One problem that will be similar to mine is Andrew Xayamongkhon's on nitric oxide and muscle growth. Andrew's problem looks at the effectiveness of nitric oxide in muscle building compounds and their health effects. He will measure levels of nitrate and nitrite found in blood. His hypothesis states that nitric oxide in these supplements is not effective for muscle growth.
Another problem similar to mine is Vinh Tran's examination of triclocarban in human urine. TCC, an antimicrobial agent, is found in many soaps, but can have adverse health effects. His hypothesis states that TCC levels will increase in people who have greater exposure to TCC through soaps. He will measure levels of TCC in urine.
One similar study between my problem and these two problems is the determination of total content of the analyte in the matrix. We all have complex matrices, and we will need to determine the content of our compounds from this complexity. Additionally, we all are working with health risks associated with compounds that have intended health benefits. We will have to determine what levels of these compounds are associated with said risks.
However, it will be very different establishing controls for our analytes. While I can easily examine energy drinks that lack taurine as a negative control, it will be harder for Vinh and Andrew to determine baseline levels of their analytes in biological fluids. I will also be able to add standard taurine to energy drinks as a positive control, something that will be harder to do for my two peers.
Chemical Structure and Standards
Standards for taurine can be purchased through Abblis Scientific. 100 grams can be purchased for $37 (catalog number AB1002120). This standard has a purity of greater than 99%.
CAS Number: 107-35-7: 2-Aminoethanesulfonic acid. http://www.abblis.com/product_AB1002120.html?&referrer=chemexper (accessed Oct 25, 2011).
For taurine analysis, gas chromatography, HILIC, and ion-exchange chromatography are all feasible methods. Reverse phase is not suitable because taurine is very polar, and it would not be retained at all by the stationary phase in a reverse phase column. Taurine is too small to be considered for size-exclusion, and lacks a suitable ligand for affinity chromatography. Finally, its lack of chiral centers makes chiral chromatography a poor choice. However, derivatization of taurine to produce a fluorescent molecule makes reverse phase chromatography a possibility as well.
Of the methods above, reverse phase chromatography of a taurine NBD-F or taurine NBD-Cl derivative is the best option. This method is simple and provides good separation from the numerous other compounds found in the matrix. Additionally, the derivatized compounds make detection simple.
A suitable column for this separation would be would be a Bondclone column with a length of 300 mm and a diameter of 3.9 mm packed with C18 chain silica particles. (catalog number WAT027324) The particles are 10 micrometers. For this separation, the pH should be kept as close to 9 as possible, and a temperature between 25 and 40 degrees is suitable. The separation should use a mobile phase of THF, acetonitrile, and phosphate buffer in a volume ratio of 4:24:72 at a pressure of 1100 psi and a flow rate of 1 mL/min.
For detection, a fluorometer should be used, since the derivatized compound exhibits activity. Such a detector provides for easy quantification, because only the taurine compounds fluoresce at the selected wavelengths, plus this method produces and better S/N ratio than uv-vis absorption. An example of such a detector is Shimadzu SPD-M10AVP diode array detector.
McMahon, G.P.; O'Kennedy, R.; Kelly, M.T. High-performance liquid chromatographic determination of
taurine in human plasma using pre-column extraction and
derivatization. J. Pharm. Biomed. Anal.[Online] 1996, 14, 1287-1294. http://www.sciencedirect.com.ezp1.lib.umn.edu/science?_ob=MiamiImageURL&_cid=271442&_user=616288&_pii=073170859501697X&_check=y&_origin=&_coverDate=30-Jun-1996&view=c&wchp=dGLzVBA-zSkzk&md5=ada4407c4aeec0327c7acd073b2c28f8/1-s2.0-073170859501697X-main.pdf(accessed Nov 3, 2011).
Sawabe, Y.; Tagami, T.; Yamasaki, K. Determination of Taurine in Energy Drinks by HPLC Using a Pre-column Derivative. J. Health Si.[Online] 2008, 54, 661-664. http://jhs.pharm.or.jp/data/54%286%29/54_661.pdf(accessed Nov 10, 2011).
Bondclone. http://www.brechbuehler.ch/fileadmin/redacteur/pdf/columns-sampleprep/lc-columns/zhbdc.pdf (accessed Nov 10, 2011).
Suitable capillary electrophoresis techniques for determining the taurine content in energy drinks include CZE and cIEF. MEKC is not suitable because most of the compounds dissolved in water-based energy drinks are highly hydrophilic. There simply would not be great enough separation between taurine and most of the other compounds in the matrix. CGE incorporates a size-related separation that is inappropriate for this study. Most of the compounds in energy drinks are quite similar in size to taurine. Focusing on the charge/size ratio will better separate taurine from other compounds, like caffeine.
Between CZE and cIEF, CZE is a better option for taurine analysis. When using cIEF for analysis, derivatization of compounds is not very suitable for the band formation in the gradient. Since taurine is most easily detected in a derivative form, CZE, which allows for this, is the better choice.
Suitable conditions for this analysis include a sodium phosphate buffer to a pH of 11.8. An applied electric field of 22 kV will produce a suitable separation in an uncoated fused-silica capillary with an internal diameter of 75 micrometers and an effective length of 40 cm.
Since CZE allows for derivatization, a fluorometer would be a suitable detector. Fluorescence is a good technique for measuring taurine because it is a selective method that has minimal interference from other compounds in the matrix and has a better signal to noise ratio than uv-vis absorbance. Given the quantity of taurine claimed to be included in energy drinks, fluorescence should not provide any issues with limits of detection. Additionally, fluorometers have proven to have high reproducibility in detecting taurine in CZE in previous studies.
Zinuella, A.; Sotgia, S.; Scanu, B.; Chessa, R.; Gaspa, L.; Franconi, F.; Deiana, L.; Carru, C. Taurine determination by capillary electrophoresis with laser-induced fluorescence detection: from clinical field to quality food applications. Amino Acids[Online] 2009, 1, 35-41. http://www.ncbi.nlm.nih.gov/pubmed/18193477(accessed Nov 20, 2011).
Although taurine can be reduced, this process is extremely difficult to carry out and would not provide an accurate way to quantify the taurine content. Therefore, an ion selective electrode would prove much more useful for quantification.
Carbon-disk electrodes respond to taurine in a system. A 300 micrometer carbon-disk electrode can serve as the working electrode, while SCE provides a suitable reference electrode.
Cao, Y.; Zhang, X.; Chu, Q.; Fang, Y.; Ye, J. Determination of Taurine in Lycium Barbarum L. and Other Foods by Capillary Electrophoresis with Electrochemical Detection. Electroanalysis[Online] 2003, 15, 898-902. http://onlinelibrary.wiley.com.ezp2.lib.umn.edu/doi/10.1002/elan.200390112/pdf (accessed Dec 6, 2011).
Nanotechnology is a rapidly growing field with great potential for many applications. One of the most common commercial uses of nanoparticles is in sunscreen, which often includes zinc oxide (ZnO) and titanium dioxide (TiO2) nanoparticles instead of using them in bulk form. As nanoparticles, these materials are transparent to visible light instead of leaving a white paste on the skin when applied, and they may also be more efficient at scattering UV light.
However, the impact of nanoparticles on human health and the environment is not fully understood. In general, the high surface-area-to-volume ratio of nanoparticles gives them different properties from bulk materials, and their size can enable them to permeate cells. Some forms of TiO2 are photocatalytic, generating free radicals when exposed to UV light and potentially damaging nearby molecules or cells.
To determine whether nanoparticles are safe for commercial applications like sunscreen, it is important to understand what happens when humans are exposed to them. Previous studies have found a small concentration of Zn ions, but no nanoparticles, in blood after exposure to sunscreen containing ZnO. Also, TiO2 nanoparticles have been shown to aggregate in the top layers of skin (stratum corneum) with little penetration deeper into the epidermis.
My hypothesis is that nanoparticles will not be detected in blood, and that both ZnO and TiO2 nanoparticles will only be present in the top layers of skin after sunscreen is applied. I would expect the amount and depth of penetration to depend on the frequency and duration of sunscreen application, nanoparticle concentration, and nanoparticle size. The analytes in this problem are ZnO and TiO2 nanoparticles of varying sizes, and the matrices under consideration are human skin and blood.
1. Biello, D. Do Nanoparticles and Sunscreen Mix? Scientific American, August 20, 2007.
2. Wolf, L. K. Scrutinizing Sunscreens. Chem. Eng. News 2011, 89, 44-46.
Blog 2: UV-vis Absorption Spectrometry
Metal oxide nanoparticles absorb light in the UV range, but they also scatter light. This property makes their UV-visible absorption spectra very complicated. The maximum wavelengths of absorption depend not only on the material, but also on the particle size and shape (3). Metal oxide nanoparticles are also difficult to quantify using UV-vis absorbance spectrometry, since their molar absorptivity also varies significantly with particle size and shape (4). Consequently, there are no convenient reference values for the maximum absorption wavelengths and molar absorptivities, although some size-dependent data and sample values were found.
3a) Bulk ZnO absorbs at 365 nm, and smaller nanoparticles in ethanol absorb at shorter wavelengths (about 340 nm for 5-nm ZnO, and 310 nm for 2.5-nm ZnO) (3). TiO2 nanoparticles of the same size in water absorb in a similar range, 340 to 370 nm (5).
3b) The value of ε for ZnO nanoparticles ranges from 35 m3/kmol mm (350 M-1cm-1) for 2-nm particles to 55 m3/kmol mm (550 M-1cm-1) for 10-nm particles (3). I could not find a value for comparable TiO2 nanoparticles.
3. Segets, D.; Gradl, J.; Taylor, R. K.; Vassilev, V.; Peukert, W. Analysis of Optical Absorbance Spectra for the Determination of ZnO Nanoparticle Size Distribution, Solubility, and Surface Energy. ACS Nano 2009, 3, 1703-1710.
4. Contado, C.; Pagnoni, A. TiO2 in Commercial Sunscreen Lotion: Flow Field-Flow Fractionation and ICP-AES Together for Size Analysis. Anal. Chem. 2008, 80, 7594-7608.
5. Kormann, C.; Bahnemann, D. W.; Hoffmann, M. R. Preparation and Characterization of Quantum-Size Titanium Dioxide. J. Phys. Chem. 1988, 92, 5196-5201.
Blog 3: Similar Analytical Problems
Nanoparticles Accumulate in the Food Chain (Nate Vetter): The hypothesis is that silver nanoparticles in wastewater end up being transferred through the food chain. The analyte is silver nanoparticles and the matrix is wastewater, insects, and animals (not sure of specifics). This problem and my analytical problem both involve detecting nanoparticles in a biological matrix, so we will likely use many of the same techniques. Both types of nanoparticles display size-dependent UV-vis properties. However, the nanoparticle material is different and the particle size may also be different. The behavior of noble metal and metal oxide nanoparticles is likely to be similar but not identical, so some different analytical techniques may be used.
Titanium Dioxide in Masterbatch (Revy Saerang): The hypothesis is that TiO2 particles in Masterbatch affect the uniformity of mixing and pigment distribution. The analyte is TiO2 nanoparticles and the matrix is a mixture of polymer resin, additives, and other pigments. Both of our analytical problems involve TiO2 nanoparticles used commercially, so it is very likely that the same techniques would be used for both problems. However, the context and matrices are different. While Revy is considering how TiO2 nanoparticles affect the properties of a mixture used in industry, I'm looking at whether TiO2 nanoparticles are absorbed through human skin. Detecting TiO2 nanoparticles in Masterbatch may require different techniques from detecting them in blood and skin, especially since skin is a solid.
Blog 6: Chemical structure and Standards
ZnO has the wurtzite crystal structure in its most common form. TiO2 commonly exists in both rutile and anatase structures, although rutile is more stable and consequently more common. Most of the references I have previously cited used wurtzite ZnO or rutile TiO2 nanoparticles, although some extracted nanoparticles from commercial sunscreens and didn't specify the crystal structure.
Images from Wikipedia: http://en.wikipedia.org/wiki/File:Rutile-unit-cell-3D-balls.png and http://en.wikipedia.org/wiki/File:Wurtzite_polyhedra.png
ZnO and TiO2 nanoparticles are commercially available in the 10-30 nm size range used in sunscreen:
Nanostructured & Amorphous Materials, Inc.
spherical ZnO nanoparticles (99.5%, average diameter 20 nm) - stock # 5810HT, $70/100 g
needle-like TiO2 nanoparticles (rutile, >98%, 10x40 nm) - stock # 5480MR, $80/100 g
SkySpring Nanomaterials, Inc.
spherical ZnO nanoparticles (99.8%, diameter 10-30 nm), product # 8410DL, $64/100 g
spherical TiO2 nanoparticles (rutile, 99.5%, diameter 10-30 nm), product # 7920DL, $64/100 g
Nanotechnology has many uses and purposes in today's world. Silver nanoparticles are being used in wound dressings, catheters, and various household products due to their antimicrobial activity. Despite the rapid progress and early acceptance of nanobiotechnology, little research has been conducted to evaluate the impact of nanoparticles on terrestrial ecosystems, despite the fact that land application of biosolids from wastewater treatment will be a major pathway for the introduction of manufactured nanomaterials to the environment. New evidence has linked nanoparticles accumulating in caterpillars in concentration magnitudes greater than the concentrations found in what the caterpillars consumed. The caterpillars can't shed the nanoparticles in an efficient manner. This can cause great concern for predators later in the food chain.
My hypothesis is silver nanoparticles can end up in the drainage, sewage, and waste water we expel which can make its way to the terrestrial ecosystems. In turn animals and insects alike, can uptake these nanoparticles and the nanoparticles can translate up the food chain as predators eat the prey. This trend will eventually lead back to humans. The results of this study should demonstrate trophic transfer and biomagniﬁcation of silver nanoparticles from a primary producer to a primary consumer.
UV-Vis absorption spectrometry
Not all silver nanoparticles are the same. In this example silver nanoparticles vary in size from 6 to 20 nm. The nanoparticles absorb at about 400 nm with a defined peak. Increasing the particle size shifts the λmax higher. Using this knowledge can allow for pin point accuracy in determining particle size in the sample. This can only occur however if the distribution of the particle size is known.
The molar extinction coefficient is roughly 2 × 10^14 M^-1 cm^-1. Note that at this value a molar extinction coefficient silver nanoparticles is much larger than a typical organic molecule.
Chemical structure and standards
I am looking specifically for Ag0 in this analytical problem and not for any species of silver. The nanoparticle range however will be in the 5-20 nanometers.6
Table 1. Silver nanoparticles in aqueous solution and toluene
Cat. No.------------ Description ----------------Size (nm)---- Quantity (mL)-----Price/USD
SNP0001-10 In aqueous, 0.1 mM Ag --------------10-------------- 20--------------- 280.00
SNP0001-20 In aqueous, 0.1 mM Ag --------------20-------------- 20--------------- 280.00
SNP0001-30 In aqueous, 0.1 mM Ag --------------30-------------- 20--------------- 280.00
SNP0001-40 In aqueous, 0.1 mM Ag --------------40-------------- 20--------------- 280.00
SNP0001-50 In aqueous, 0.1 mM Ag --------------50-------------- 20--------------- 280.00
SNP0002-10 In toluene, 0.1 mM Ag -------------5~10----------- 20--------------- 380.00
1. AshaRani, P. V.; Kah Mun G. L.; Hande M. P.; Valiyaveettil, S. Cytotoxicity and Genotoxicity of SilverNanoparticles in Human Cells. ACS Nano, 2009, 3 (2), 279-290
2. Jensen, T.; Schatz, G.C.; Van Duyne, R. P. Nanosphere Lithography: Surface Plasmon Resonance Spectrum of a Periodic Array of Silver Nanoparticles by Ultraviolet−Visible Extinction Spectroscopy and Electrodynamic Modeling. J. Phys. Chem. B. 1999, 103, 2394-2401
3. Judy J. D. ; Unrine J. M. ; Bertsch P. M. Evidence for Biomagnification of Gold Nanoparticles within a Terrestrial Food Chain. Environ. Sci. Technol. 2011, 45, 776-78
4. Lim, S. F.; Riehn R.; Ryu W. S. ; Khanarian N. ; Tung C. ; Tank D. ; Austin R. H. In Vivo and Scanning Electron Microscopy Imaging of Upconverting Nanophosphors in Caenorhabditis elegans. Am. Chem. Soc. 2006, 6, 169-174
5. Link, S.; Wang, Z.L.; El-Sayed, M.A. Alloy Formation of Gold-Silver Nanoparticles and the Dependence of the Plasmon Absorption on Their Composition. J. Phys. Chem. B. 1999, 103, 3529-3533
6.Journal of Nanobiotechnology. Silver nanoparticles. http://www.jnanobiotechnology.com/content/3/1/6/figure/F1?highres=y(accessed Oct 26, 2011)
7.Nanocs. Silver nanoparticles. http://www.nanocs.com/Silver_nanoparticles.htm (accessed Oct 26, 2011)
Similar Analytical Problem(s)
Abdihakim Abdullahi - Mercury in Skin Creams
His hypothesis is the mercury in cosmetic products cause many health issues especially pertaining to minority communities. His analyte is mercury and his matrix is skin creams. Both of our problems require the use of many samples to create calibration curves to compare our unknowns to. Both problems require the separation of our analytes from the matrix they reside in to obtain good spectrums in the uv-vis range. Our problems vary in that I will need one control and I will be using known concentrations in the soil samples as well as a calibration curve to find concentrations in the tissues. Whereas Abdihakim will need no control and some samples to provide a calibration curve along with his unknown analytes.
Similar analytical problem: Exposure to Zinc Oxide and Titanium Dioxide Nanoparticles in Sunscreen
Trichloroethylene and Tetrachloroethylene are resistant to breakdown by biological processes, which causes them to accumulate in soil and groundwater. These chlorinated hydrocarbons are released into the air as vapors and find their way into the indoor air of overlying homes and buildings. Relatively low concentrations of these volatile compounds can cause major indoor problems and are a health risk. They need to be able to be detected in the vapor form to decide whether land can be developed or added to the Superfund National Priority List for bioremediation.
The hypothesis is that these compounds are being released into the environment by industrial plants because of improper disposal. Trichloroethylene was used for many years in dry cleaning until the mid 1960's when its toxicity was called into question and it was replaced by halothane. Tetrachloroethylene was also used widely in dry cleaning and textile processing until recently when its safety was also questioned.
1. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Tetrachloroethylene (Update). U.S. Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA. 1997.
2. Hanson, D. J. (2011). EPA moves on vapor intrusion. Chemical and Engineering News, 89(16), 32-34.
UV-Vis absorption spectrometry
Reagent grade TCE (trichloroethylene) in distilled, deionized water has a molar absorptivity of less than 10 L/mol cm for wavelengths longer than 260 nm, absorbances less than 4x10^-3, a concentration of 50 ppm, and a path length of 1.3 cm (1).
PCE (tetrachloroethylene) has a molar absorption coefficient of 225 L/mol cm at 254 nm in an aqueous solution of water (3).
PCE has a maximum wavelength, where the absorbance for a 10 mm pathlength of solvent exceeds 0.05 absorbance unit, of 320 nm. TCE has a maximum wavelength that slightly exceeds 400 nm under the same conditions (2).
1. Ahmed, Sohailuddin; Ollis, David F. Solar Photoassisted Catalytic Decomposition of the Chlorinated Hydrocarbons Trichloroethylene and Trichloromethan. Solar Energy 1984, 32, pp 597-601
2. Kaye and Laby Tables of Physical and Chemical Constants, http://www.kayelaby.npl.co.uk/chemistry/3_8/3_8_7.html (accessed 9/29/11).
3. Mertens, Ralf; Sonntag, Clemens von. Photolysis of Tetrachloroethene in Aqueous Solution. Journal of Photochemistry and Photobiology 1995, 85, pp 1-9.
Similar Analytical Problems
My analytical problem is similar to Shengsi Liu's CO Detections in Post Combustion Fuel. His matrix is fuel exhaust fumes and his hypothesis is that the exhaust of internal combustion engines contains a slight amount of CO which can be collected and analyzed in order to find the concentration of CO per volume. This is important because of the toxicity of carbon monoxide and its contamination of air quality. My problem is also similar to Nur Marzuki's Liquified Petroleum Gas in insecticide aerosol. Her analyte is LPG and her matrix is the insecticide aerosol. This is important to find also because of health reasons. Insecticide is sprayed directly on to the skin and absorbed into the bloodstream. If hazardous chemicals are being absorbed it is imperative to know so that a safer compound can be employed in the spray.
Our studies should be similar because we are all testing the concentration of a vapor in the air. Shengsi also has a similar analyte. They are both carbon based with relatively small molecular weights.
Nur, Shengsi and my studies will differ because they are both studying a matrix where the analyte is always present and can fairly easily be tested for. My analyte may not always be present in the vapor form even if it is present in the soil or groundwater. It is important to measure it in the vapor form because land contaminated with my analytes, TCE and PCE, can not be put on the National Superfund list for remediation unless these chemicals are present in the vapor form. Our studies will also differ because we have different matrices. Nur is dealing with the other components contained in aerosol sprays and Shengsi has to account for the other compounds in exhaust fumes, whereas my matrix is the air.
Studies needed to investigate my analytical problem
Hypothesis: TCE and PCE are being released into the environment because of their improper disposal by industrial plants utilizing them for dry cleaning products, metal degreasing, pharmaceutical production, weapons production, and pesticide formation.
(A) Identify soils and water that test positive for TCE and PCE. (There is already a list of known contaminated sites created by the EPA)
(B) Measure TCE and PCE vapor levels in regions of known contaminated soil and groundwater as well as known uncontaminated soil and groundwater (areas in forests not near buildings or weapons testing sites).
(C) Based on levels found, create a study in the laboratory to figure out how much TCE and PCE are released as vapors when soil or groundwater are contaminated.
(D) Create a calibration curve that represents ppm of analyte in groundwater or soil versus ppm of analyte in the air above groundwater or soil. This is important because land contaminated with PCE and TCE can only be put on the national superfund list for remediation if the air is contaminated, not the soil.
(E) Study how TCE and PCE are released into the air from soil or groundwater and in what concentrations.
(F) Figure out which factors increase the rate of TCE and PCE being released into the air.
Slight lightheadedness was reported by six male volunteers exposed to PCE at a concentration of 210-240 ppm for over 30 minutes. Increased host (mice) susceptibility to pulmonary bacterial infection occured after a 3-hour inhalation exposure to 50 ppm PCE. 63% of male mice developed hepatocellular carcinoma compared to the control at 35% when exposed to 100 ppm PCE for 103 weeks. Because of this I would put the detection level in air at 50 ppm.
1. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Tetrachloroethylene (Update). U.S. Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA. 1997.
While the chlorine atoms in Trichloroethylene and tetrachloroethylene can be used as quenching agents in other molecules, TCE and PCE by themselves do not fluoresce. Neither TCE nor PCE have conjugated double bonds that are necessary for fluorescence. One article suggested adding a fluorescent dye such as Red Nile, which is TCE soluble but water insoluble. While this does make the molecule fluoresce, it is ineffective for distinguishing TCE and PCE from impurities when the analytes are found in a soil matrix. As a control, Freon 113 and pure TCE samples were added to previously centrifuged TCE contaminated soil samples. Most of the samples contained large numbers of shell fragments that fluoresced. Because of this, the minimal amount of TCE in the sample could not be distinguished from the impurities.
TCE is an alkene that will have a =C-H bend somewhere between 995-685 cm-1. Unfortunately this is in the fingerprint region and could be difficult to identify. Both TCE and PCE have a medium C=C stretch between 1680-1620 cm-1. Alkenes are very common compounds and an IR soil sample containing TCE or PCE could also contain numerous other alkenes. TCE and PCE found in the air will most likely not have other alkenes present because air contains approximately 20.95% oxygen, 0.03% carbon dioxide, 0.93% argon, and 78.09% nitrogen. None of these air components are an alkene. Because of this gas chromatography/ Fourier transform infrared spectroscopy could be used.
Because it is so difficult to distinguish the difference between dyed TCE and dyed PCE and other contaminants in soil I would not recommend any instrument that measures fluorescence. I'm not sure how you would dye TCE and PCE vapor that is released from soil, so there wouldn't be any way to make it fluoresce. Because of this I would recommend gas chromatography/ Fourier transform infrared spectroscopy to detect TCE and PCE in the air.
1. Griffin, Terry W.; Watson, Kenneth W. A Comparison of Field Techniques for Confirimg Dense Nonaueous Phase Liquids. GWMR. 2002, 22, 48-59.
2. Mohrig, Jerry R.; Hammond, Christina N.; Schatz, Paul F. Techniques in Organic Chemistry, 3rd ed.; W.H. Freeman and Company: New York; pp 464.
3. Smith, James S. Does Peer Review Mean That the Paper Is Scientifically Defensible? Trillium. 2002, 5, 1-5.
Chemical structure and standards
Sigma-Aldrich sells 5 mL analytical standard TCE, for environmental analysis (Fluka) for $38.60
catalogue number: T1115 (WWW Chemicals)
Sigma-Aldrich also sells 5 mL analytical standard PCE for $37.20
catalogue number T1023 (WWW Chemicals)
Sigma-Aldrich. http://www.sigmaaldrich.com/catalog/ProductDetail.do?lang=en&N4=02666|FLUKA&N5=SEARCH_CONCAT_PNO|BRAND_KEY&F=SPEC (accessed Oct 24, 2011)
http://www.chem.com/catalogs/ (accessed Oct 24, 2011)
For my analytical problem, gas chromatography would be the best choice for analysis. Both TCE and PCE need to be detected in the vapor form. Because the matrix is air, size-exclusion chromatography doesn't make much sense. Neither does chiral chromatography since the analytes are not chiral. It would be difficult to use any other form of chromatography since the analytes must be in the vapor form and are in ppb concentrations in the air.
A Supelco Equity-5 capillary column (30 m long, 0.25 mm inner diameter, 0.25 µm ﬁlm thickness, Sigma-Aldrich) could be used. They can be purchased from Sigma-Aldrich for $450.00 (catalogue number 28089-U). An AS 2000 autosampler (Fisons) can be used with Helium as the carrier gas with a constant column head pressure of 60 kPa. The temperature is programmed to 40 °C for 7 minutes and then ramped to 130 at 30 °C/min and held for one minute. A quadripole MS system can be used to detect TCE and PCE levels using flame ionization. Flame ionization is ideal because of its sensitivity to hydrocarbons. It is not an issue that the sample is destroyed because it is not needed for further analysis.
Some indoor and above soil air samples were found to have interfering VOCs that could not be chromatographically removed. Because of this they require 2-D GC separation using DB-Wax as a polar phase and DB-MTBE as the nonpolar phase. This required the use of an aluminum oxide/ sodium sulfate PLOT column that is 50 m in length and 0.32 mm inner diameter. Ambient air samples can be acquired at a flow rate of 15 mL/min for 40 min. Quantification was also be performed using flame ionization and a q-MS system.
1.Aeppli, Christoph; Holmstrand, Henry; Andersson, Per; Gustafsson, Orjan. Direct Compound-Speciﬁc Stable Chlorine Isotope Analysis of Organic Compounds with Quadrupole GC/MS Using Standard Isotope Bracketing. Anal. Chem. 2010, 82, 420-426.
2.Air and Waste Management Associtation. Field Method Comparison between Passive Air Samplers and Continuous Monitors for VOCs and NO2 in El Paso, Texas. J. Air and Waste Manage. Assoc. 2004, 54, 307- 319.
4.Kim, Sun Kyu; Chang, Hungwei; Zellers, Edward T.; Microfabricated Gas Chromatograph for the Selective Determination of Trichloroethylene Vapor at Sub-Parts-Per-Billion Concentrations in Complex Mixture. Anal. Chem. 2011, 83, 7198-7206.
BLOG 10. Problems using similar techniques
My preferred technique is GC-FTMS. Other analytical problems that are using the same technique are Nur Marzuki and Melissa Eubanks. Nur is using GC-MS to detect liquefied petroleum gas in insecticide aerosol, while Melissa is also using GC-MS to detect silicones (decamethylcyclopentasiloxane) in drain water and marine organisms.
Blog 11. Capillary electrophoresis technique
I could not find any instances where TCE or PCE were measured in the environment by way of capillary electrophoretic separations. Measuring it as a gas would be extremely difficult using this method if at all possible. If you were to measure their concentrations in a soil sample, the sample would have to be ground up extremely small to be able to fit into the tube. It is possible that the soil sample could be soaked in water and then the soil is filtered out, but I'm not sure how much of the soluble TCE and PCE would be in the filtrate and how much would still be present in the soil sample.
If a method was found to prepare a sample for my analytical problem I would not use cIEF because TCE does not have a proton to give up or the ability to receive one. MEKC would make distinguishing my analytes from each other difficult since they are so close in size. I would not use CGE because I don't believe it is possible to get the gas into the gel. Because of all these limitations I would use CZE with an MS detector, but I do not believe this is a reliable source for measurement. I would use an MS detector because of the low level of analytes that will be present in the sample.
BLOG 13. Analytical electrochemistry
TCE and PCE are not electroactive. Because of this I would use a conductivity detector in a chromatography column. This sensor consists of two electrodes that are housed in a glass flow cell. One electrode is grounded. The detector can sense an electrical impedance when ions move through the sensor cell, allowing for the collection of data.
An AC voltage is used when running a current across the electrodes in order to avoid electrode polarization. This occurs with DC voltage because of the generation of gases at the electrode surface.
For an electrical conductivity detector a sensitivity of 5x10^-9 g/mL is expected. The linear dynamic range is around 5x10^-9 to 1x10^-6 g/mL and the response index is 0.97 to 1.03.
Scott, Raymond P. W.; Ion Chromatography: The Electrical Conductivity Detector. http://www.chromatography-online.org/ion-chromatography/Detectors-for-Ion-Exchange-Chromatography/The-Electrical-Conductivity-Detector.html.
My analytical problem will be a focused on the effects of Red Tide in the oceans. Red tide is a major problem for ocean wildlife, since harmful toxins get released into the oceans from clusters of algae. The algae are composed of phytoplankton, single-celled plant-like organisms that release natural toxins into the ocean's water which ends up killing the marine life. "The most common type of toxin released from the algae is brevetoxin, which has been known to cause problems for humans and marine life. It can be harmful to humans because people who live near the ocean, spend a lot of time in the ocean, breathe in the toxin that gets released into the water vapor (1)." The marine life cycle suffers because the toxin affects all organisms from the small microscopic organisms to the larger fish that consume the smaller organisms (1)." Since the fish get contaminated with the toxin, the fishing communities that surround the ocean suffer because the fish can no longer be consumed or if people consume the fish they get sick.
The main problem I want to look at deals with the toxicity of the water. How toxic is brevetoxin and more importantly, what toxicity levels of brevetoxin would be harmful to the marine life? Is the toxicity level different for being harmful to humans? Are there any other toxins that can be blamed?
There will be other toxins that can be found in the ocean water samples but the most prevalent toxin found in the water will be brevetoxin, which is supported by multiple scientific experiments. The best place to gather water samples would be found where there are several species of fish washed up on the shore.
The analyte in my analytical problem is the brevetoxin or other lesser known toxins that are extremely harmful to the environment. The matrix is the ocean water and any other contaminants that are found in the water.
UV-Vis Absorption Spectrometry
Scientists primarily use multi-wavelength spectroscopy to measure brevetoxin levels in ocean water. "Multi-wavelength spectroscopy is a versatile, rapid and reliable tool that has immediate applications as a biosensor for the detection, identification and enumeration of pathogens. The sample information contained in a typical multiwavelength ultraviolet/visible (UV/vis) spectrum includes cell size, chemical composition and shape. This information is obtained from the spectroscopic analysis of a sample measured over a broad range of wavelengths (200 - 900 nm) with scattered light measured at one or many different angles (3)." Multi-wavelength spectroscopy just became the primary tool to measure various toxin levels in ocean water, including brevetoxin, within the last ten years.
The range of wavelengths that are primarily used in every experimental procedure is 200 to 900 nm. In the Forward, Tester, and Cohen journal, "the Karenia brevis and a local, non-toxic isolate of Prorocentrum minimum were grown in filtered Gulf Stream seawater diluted with distilled water to a salinity of 30, enriched with f/2 nutrients at 22 degrees Celsius(4)." The f/2 nutrients are added to the ocean water and keeps the original sample clear of any contaminants that may effect the results of the experiment. The temperature and specific salinity of the ocean water may vary depending on what the scientist wants to study. Pure ocean water with a certain salinity would be used as the control (blank) of the experiment and various concentrations would be used to obtain multiple absorbances. The exact values for the molar absorptivity or optical density were never found from my research.
Similar Analytical Problem
John Raia - Detection of Anionic Surfactants in Water -
His hypothesis is that anionic surfactants should be present in higher concentrations in areas that have been exposed to dispersant chemicals compared to other natural water sources with no known history of intentional contamination. The analyte is anionic molecules like sodium lauryl sulfate or sodium octanesulfonate, which can be found in an ocean water matrix.
Our analytical problems are similar because our samples will be taken from the same matrix, the ocean. Not only do we both use the ocean water as the matrix, but we both can use a version of UV-Visible Spectrometry in order to test our samples for our desired product, for John it's the sodium lauryl sulfate or sodium octanesulfonate and for me it would be brevetoxin.
Our analytical problems are different because one of the analytical methods that I will use for my experiment is a multiwavelength spectrometer. The multi-wavelength spectrum includes cell size, chemical composition and shape of the sample that I will be studying.
Chemical Structure and Standards
The brevetoxin standards can be found on the CalBioChem / EMD4Biosciences company webpage.
Catalog Number - 79580-28-2
Quantity - 100 microliters
Purity - >95%
Price - $449
Catalog # - 85079-48-7
Quantity - 100 micrograms
Purity - >95%
Price - $499
EMD4Biosciences. 203732 Brevetoxin PbTx-2, Ptychodiscus brevis. http://www.emdchemicals.com/life-science-research/brevetoxin-pbtx-2-ptychodiscus-brevis/EMD_BIO-203732/p_F8eb.s1LILsAAAEWlWEfVhTm?WFSimpleSearch_NameOrID=brevetoxin&BackButtonText=search+results. (Accessed Oct, 23rd
EMD4Biosciences. 203734 Brevetoxin PbTx-3, Ptychodiscus brevis. http://www.emdchemicals.com/life-science-research/brevetoxin-pbtx-3-ptychodiscus-brevis/EMD_BIO-203734/p_F8eb.s1LILsAAAEWlWEfVhTm?WFSimpleSearch_NameOrID=brevetoxin&BackButtonText=search+results. (Accessed Oct, 23rd)
Atomic and Mass Spectrometry
The ESI-MS/MS spectrum of Brevetoxin PbTx-2 in 0.002 M HCl in a methanol:water (4:1 ratio) solution is shown in the figure below (the graph on top)
References for mass spec.
Hua, Yousheng. Cole, Richard B. Electrospray Ionization Tandem Mass Spectrometry for Structural Elucidation of Protonated Brevetoxins in Red Tide Algae. http://pubs.acs.org/doi/full/10.1021/ac990433o. (Accessed October, 26th)
1. Ramsdell, John. Science Daily. Aerosol Toxins from Red Tides May Cause Long-Term Health Threat. July 9, 2008. http://www.sciencedaily.com/releases/2008/07/080709110049.htm (Accessed Sept. 16th, 2011)
2. Anderson, Dr. Don. Harmful Algae. May 31, 2011. http://www.whoi.edu/redtide/ (Accessed Sept 16, 2011)
3. Mattley, Yvette D. Garcia-Rubio, Luis H. Multiwavelength Spectroscopy for the Detection, Identification and Quantification of Cells. Nov. 5th, 2000. http://www.marine.usf.edu/sapd/spiep00ym.pdf (Accessed Sept. 26th, 2011)
4. Cohen, Jonathan H. Tester, Patricia A. Forward Jr., Richard B. Oxford Journals: Journal of Plankton Research. Sublethal Effects of the Toxic Dinoflagellate Karenia Brevis on Marine Copepod Behavior. January 12th, 2007. http://plankt.oxfordjournals.org/content/29/3/301.full (Accessed Sept. 26th, 2011)
Blog 9- Chromatographic Techniques
1. Reverse Phase chromatography can be used while gas chromatography and HILIC probably could be used in some similar experiments. Gas chromatography would be more helpful if I were analyzing the Brevetoxin levels in the air composition from the ocean water. HILIC could probably be used but I don't think it would help to deal with more water in the process since the sample is already in ocean water. Ion exchange chromatography will not be used because my analyte is not an element and doesn't have ions present. Size exclusion chromatography is usually used for macromolecules and my analyte would not show good results from SEC. Affinity chromatography is mostly used for biochemistry experiments that relate antibodies to antigens, enzyme to substrate, or receptor to ligand and my analyte does not deal with those types of interactions. Chiral chromatography will not be used because my analyte does not have chiral centers.
2. My first choice of chromatography would be reverse phase liquid chromatography. Reverse phase liquid chromatography will be useful because since the stationary phase in non-polar and my analyte is polar, this will create a good separation. Reverse phase chromatography is almost always used for experiments that are analyzed by liquid chromatography .
3. The columns that will be used are "C18 "Aqua"column [3 μm, 125 A, 75 × 200 mm, (Phenomenex #003-4311-B0, Torrance, CA)] and C18 guard column (Phenomenex #AJO4287, Torrance, CA) (Yung, McDonald)." The stationary phase is C18 in a fully porous silica, with a particle size of 3 microliters and the pore size is 125 A. The column length is 30mm with an internal diameter of 2mm. The column temperature was set to 32 degrees Celsius. I could not find any value for the typical backpressure used in the column.
4. The mobile phase will be made up of purified water (solvent A) and methanol:1 mM acetate (solvent B). "The solvents were operated on the following time cycle: 20% B for 0-1 min, linear gradient to 90% B at 3 min, 90% B 3-10 min, 20% B for 10.1-12.5 min (Yung, McDonald)."
5. The detector that will be used is an MS/MS. The MS/MS will be used because since the different forms of Brevetoxin have molecular weights very similar to one another, the use of MS/MS will be able to separate the different types of Brevetoxin.
6. Not Available
(1) Yung Sung Cheng. McDonald, Jacob D. "Concentration and Particle Size of Airborne Toxic Algae (Brevetoxin) Derived from Ocean Red Tide Events." National Institutes of Health. May 15, 2005. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2652738/ (Accessed November 1, 2011)
(2) Phenomenex. "C18 "Aqua"column [3 μm, 125 A, 75 × 200 mm, (Phenomenex #003-4311-B0) and C18 guard column (Phenomenex #AJO4287)" Phenomenex-DNV. Torrance, CA. 2011. http://www.phenomenex.com/Products/Part/00A-4311-B0 (Accessed November 9th, 2011)
Blog 11 - Capillary Electrophoresis Techniques
1. The CE techniques that would work for my analytical problem would be CZE and MEKC. The CZE technique will be able to separate the brevetoxins from the ocean water matrix but it would be hard to separate the different types of brevetoxin from each other. The cIEF technique would not be useful for my analytical problem because it separates by pI. The pI is the pH of a certain molecule where the molecule has no net charge. Since the brevetoxin molecule is neutral, it will not have a varying pH under different specific conditions. The CGE technique is not useful for my analytical problem because it is used to separate charged polymers like DNA and since my analyte is neutral this is not a good technique to use.
2. The MEKC technique would be the best technique to use for my analytical problem. Since the micelles form inside the capillary tube, it creates a hydrophobic interior inside the micelle and a hydrophilic buffer solution. This will separate all the components of the ocean water. The neutral brevetoxin molecules will also separate since they can travel through the hydrophobic micelle interiors and the hydrophobic buffer solution at different rates which makes them elute from the capillary at different times.
3. In the paper referenced below from Damian Shea, they used a 50 cm x 75 micrometer ID bare silica capillary(Polymicro Technologies, Phoenix, AZ). The buffer that was used was a 10mM sodium borate / 30mM SDS / 10% methanol buffer solution at a pH of 9.3. The experiment was run with an electric field of 30kV and at a temperature of 30 degrees Celsius +/- 0.3 degrees celsius. The MEKC experiment was also run with a UV detection at 214nm.
4. The detector used for Damian Shea's experiment was laser-induced fluorescence (LIF). The LIF used was a 25 mW He/Cd laser with an excitation at 354 nm and a fluorescence emission at 410 nm. The LIF is useful because it will yield a greater sensitivity than UV detection and better selectivity of the different types of brevetoxins.
Shea, Damian. "Analysis of Brevetoxins by Micellar Electrokinetic Capillary Chromatography and Laser-induced Fluorescence Detection." Department of Toxicology. North Carolina State University. April 14, 2005. http://onlinelibrary.wiley.com/doi/10.1002/elps.1150180216/pdf. (Accessed November 19th, 2011)
My post didn't seem to work.
The analytical problem that is similar to mine is Sara's. The Geochemical Mobilization of Arsenic in Groundwater. It is similar because we are both studying a certain chemical/toxin in water. It is different because her problem deals with groundwater from wells and mine deals with the ocean.
Polytetrafluoroethene, commonly known as Teflon, is a polymer that is used in many pots and pans today to make them non-stick. To create Teflon coated pans many companies will use compounds called perfluorooctanoic acid, or PFOA, to act as a surfactant to the Teflon. It has recently been discovered that PFOA is a carcinogenic and persists in the environment for many years. Although most of the PFOA is burnt off when the pans are cured at high temperatures there are still small levels that are given off during the first few times the pans are used. As the pans used small defects can become another source of PFOA's entering the air and the food that is being cooked at the time. Due to the nature of Teflon, it is very easy to scratch pans and cause tiny defects that could later lead to PFOA entering the body or environment. Many companies have said they will no longer use PFOA's by 2015 but will continue to use Teflon. This also causes problems because when Teflon reaches certain temperatures (250oC) it begins to break down and releases a compound similar to PFOA.
UV-Vis absorption spectrometry
Teflon does not absorb in the UV-VIS range due to the fluorine in the compound. The fluorines cause Teflon to have a large band gap and would therefore require a high energy to excite the electrons. PFOA also has a low UV-VIS absorption for the same reason. To use UV-VIS absorption to detect a derivatization of PFOA must occur. One way to do this is by adding benzylamine in N2¬ and xylene using the catalyst Al2¬O3. The solution was then heated at 140°C for ten hours. The derivative was found to absorb at 248 nm or higher and had a molar absorption coefficient of 103.(2) There are not many papers found on UV-VIS absorption for PFOA and Teflon because other methods are more promising for determining if they are present such as LC/MS.(3)
Similar Analytical Problem
One analytical problem similar to mine is DEHP Leaching from PVC into Contents of Medical Devices from Rajvi Mehta. Our problems are similar because they are both polymers leaching out of other substances. Both PFOA and DEHP are detrimental to humans at high levels. Both problems have similar issues when it comes to setting up studies and tests for our analytes. Such as mine there are easily ways to get both positive and negative controls whereas hers, it may be hard to find a negative control.
Chemical Structures and Standards
From Sigma-Aldrich, 171468, 5g for $34 or 25g for $130
From Sigma-Aldrich, 430935, 5g for $35.40 or 100g for $130
Mass Spectrum using ESI-triple Quad
Kadar, H. "Comparative study of low- versus high-resolution liquid chromatography-mass spectrometric strategies for measuring perfluorinated contaminants in fish." Food additives & contaminants. Part A. Chemistry, analysis, control, exposure & risk assessment 28.9 (2011):1261.
1.King, Anthony. "Sticking point", Chemistry and Industry. 2007, 17, 24-25
2.Lindstrom, Andrew, and A B BLindstrom. "Polyfluorinated Compounds: Past, Present, and Future." Environmental science & technology 45.19 (2011):7954.
3.Huang, Ke, and KHuang. "Determination of trace PFOA in textiles with HPLC-UV spectrometry." 印染 37.9 (2011):37.
Perfluorooctanoic acid (PFOA) is a perfluoronated water and oil repellant used to treat carpeting and tile. In addition, it is used in the synthesis of polytetrafluoroethylene, also known as Teflon, as well fluoroelastomers. It has been found in elevated levels in both animals and humans, and is a known carcinogen. One of the major sources of contamination is through the waste water of factories that use PFOA.
The central hypothesis of this study is that people living or work in close proximity to sources of PFOA dumping will have dangerously elevated levels of PFOA in their bloodstream. This hypothesis is best tested by taking blood samples in potential risk areas and comparing them against a control of blood samples taken in blood banks across the nation. The analyte, PFOA, will have to be detected in the matrix, blood, quickly and efficiently. The instruments chosen to measure PFOA levels will have to be able to either filter out interfering factors.
UV-Vis Absorption Spectrometry
UV-Vis spectra for perfluorooctanoic acid is not freely available. Only IR spectra for perfluorooctanoic acid were posted to spectra databases. The carbon-fluorine bonds
are not visible in UV-Vis spectra, but the carboxyl group in isolation would have a maximum wavelength of absorption of 204 nm in ethanol. Carbonxyl's molar absorptivity is 41 L/mol*cm. Since perfluorooctanoic acid is soluble in blood, a water based matrix, it is reasonable to assume that it will be soluble in ethanol. A preliminary experiment would have to be done in order to determine if the adjacent carbon-fluorine bonds alter the absorption spectra from the prediction. Comparing two similar simple compounds, one an organic molecular and the other the perfluorinated version, would show if there is a significant effect. One possible pair is acetic acid and trifluoroacetic acid.
Separation Through Chromatography
PFOA is suitable to be extracted by several methods of chromatography. It is large enough to be seperated with size exclusion chromatography, it can be deprotonated in basic conditions and extracted with ion exchange chromatography, it can be derivatized with diazomethane and extracted with gas chromatography, or it can be extracted with reverse phase chromatography. HILIC can be used but it is not as effective as reverse phase. Affinity and chiral chromatography can not be used as the molecule has no notable stereoisomers or notable ligands.
Reverse phase chromatography is the most efficient choice of the available options. It is effective and widely used. Extraction has previously been demonstrated with a Genesis C8 column . A Genesis C8 column has a length of 50 mm, an inner diameter of 2.1 mm. It is filled with silica with a particle size of 4 μm that remains stable between pH 1 to 10 . The column can be bought from Crawford Scientific, catalog number 5109766. The mobile phase is a gradient elution of 2mM ammonium acetate in water and methanol.
The mobile phase can be directly injected into a tandem MS/MS with electrospray ionization. When measured against a standard solution of 1 μg/mL PFOA the exact levels of PFOA in the bloodstream can be quickly and accurately measured.
CZE is the most effective type of capillary electrophoresis for separating my analyte. MEKC has no benefit as my analyte contains a polar acid group and a nonpolar fluorinated hydrocarbon tail. Its preference of phase is not easily predictable. As my analyte has a pKa of approximately 0 , and is neutral normally, cIEF has no benefit either. CGE is not needed as the analyte is not a macromolecule and it is not helpful to sort by size.
The appropriate buffer for perfluorooctanoic acid is a 50 mM disodium hydrogen phosphate buffer at 9.5 pH diluted with 40% isopropanol. The capillaries should be fused silicon (75 mm ID, 30 cm total length) for optimal resolution and separation time .
While UV spectroscopy has been used as a detection method in the past, mass spectrometry is the best way to measure the concentration of the analyte. Mass spec gives a lower limit of detection and quantification than UV spec.
Suppressed Conductivity Detection
PFOA can be successfully detected in concentrations as low as 0.5 micrograms per liter by a combination of reversed-phase HPLC and suppressed conductivity detection . The PFOA is separated on a Acclaim PA2 (3 mm 2.1 x 150 mm) column using a combination of 70:30 (v:v) acetonitrile to water, 100mM H3BO3 and 9mM KOH at a pH of 8, and deionized water. The eluent was suppressed by a Dionex ASRS ULTRA II 2 mm suppressor using 25 meq/L H2SO4 at approx 0.5 mL/min as the regenerant. Once extracted, the PFOA concentration can be measured with an electrical conductivity meter and compared to a standard sample.
The perfluorooctanoic acid used to make the standards for the calibration curve will be purchased from Sigma-Aldrich. It is listed under catalog number 171468 and costs $34 for 5 grams.
Perfluorooctanoic Acid Structure
Derivatized Perfluorooctanoic Acid Mass Spectrum
Similar Analytical Problems
This problem is most similar to four other analytical problems, three which have the same matrix and one that shares an analyte. Rajvi Mehta's study of DEHP leeching from PVC, Osman Jamshed's study of prion detection, Matt Marah's study of cadmium levels in blood and my study are all conducted in a blood matrix. The other studies concentrate on different analytes however, DEHP, prions, and Cd respectively. Megan Hartmann's study of PFOA and Teflon shares the PFOA analyte with my study, however she is studying PFOA released from cookware so she has an air matrix. Matt Marah has the closest hypothesis to mine, he is testing if Cd levels are higher in the blood of people who live near plants that use Cd. My hypothesis also theorizes that analyte levels increase in people who live near a plant that uses the analyte. Rajvi Mehta's hypothesis that DEHP builds up in the human body and causes adverse effects, is based on constant exposure but also concentrates on the specific level of analyte. Osman Jamshed's hypothesis that prions are present in unregulated meat also requires the measurement of the level of an analyte but seeks to find an analyte that is naturally generated. Megan Hartmann's hypothesis that Teflon pans release PFOA differs from my hypothesis in that I seek quantitative levels and she is looking for qualitative conformation of the release of PFOA.
1. Substance flow analysis for Switzerland: Perfluorinated surfactants perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA); Federal Office for the Environment (FOEN) : Bern 2009
2. Olsen, G. Decline in Perfluorooctanesulfonate and Other Polyfluoroalkyl Chemicals in American Red Cross Adult Blood Donors, 2000−2006. Environ. Sci. Technol., 2008, 42 (13), pp 4989-4995
3. National Institute of Standards and Technology. Chemistry WebBook: Perfluorooctanoic acid http://webbook.nist.gov/cgi/cbook.cgi?ID=B6009805&Mask=80 (Accessed 9/29/11)
4. Skoog , D, Holler, J, Crouch, S. Principles of Instrumental Analysis, 6th ed.; Brooks/Cole: Belmont, CA, 2007.
5. Sigma-Aldrich Catalog, Perfluorooctanoic Acid. http://www.sigmaaldrich.com/catalog/ProductDetail.do?lang=en&N4=171468|ALDRICH&N5=SEARCH_CONCAT_PNO|BRAND_KEY&F=SPEC
6. Liu, Wen-Lin, and W. Liu. "Headspace solid phase microextraction in-situ supercritical fluid extraction coupled to gas chromatography-tandem mass spectrometry for simultaneous determination of perfluorocarboxylic acids in sediments." Journal of chromatography 1218.43 (2011):7857.
7. Flaherty, John M "Quantitative determination of perfluorooctanoic acid in serum and plasma by liquid chromatography tandem mass spectrometry" Journal of Chromatography B 819.2 (2005): 329-338
8. Jones Catalog, Genesis C8 Column, http://www.discoverysciences.com/uploadedFiles/Home/HPLCCols_OthrColsJonesCols_p64to66.pdf
9. Wójcik, L., Szostek, B., "Separation of perfluorocarboxylic acids using
capillary electrophoresis with UV detection" Electrophoresis 2005, 26, 1080-1088
10. Goss, K.-U. "The pKa Values of PFOA and Other Highly Fluorinated Carboxylic Acids (Addition/Correction)", Environ. Sci. Technol., 2008, 42 (13), pp 5032-5032
11. de Borba B., Rohrer J. "Analysis of PFOA and PFOS in Water Using Reversed-Phase HPLC with Suppressed Conductivity Detection." LC-GC Europe. March 2007;20:10
The research project was stimulated by the increasing tendency in consuming skin whitening products in the Asian beauty market. The research is important because a large number of Asian women use different kinds of whitening products to their skin every day. Sorts of anti-pigmentation compounds were added into the products, these products varies from prices and the effectiveness of whitening.
What I am going to make a comparison is the arbutin and tranexamic acid. Arbutin is widely used in the products with fair prices and the tranexamic acid is always preferred by the luxury products. The comparison will mainly focus on the whitening effects of the products with these two compounds and try to find out that the luxury component is not much better than the normal one. The hypothesis is tranexamic acid has better performance in skin whitening and more reliable to use externally.
The featured arbutin-added whitening product in the Asian beauty market is α-arbutin serials from DHC, Japan, and the tranexamic acid is mainly used by the sheiseido brand's whitening line. Thus the matrix of the analyte is whitening cream containing arbutin and whitening cream with tranexamic acid.
UV VIS ABSORPTION SPECTROMETRY
For arbutin, the maximum wavelength of the absorption is 227nm, the analyte was dissolved in the deionized water, the HPLC eluent was 40% methanol(v/v) in 0.02M phosphate buffer. however, the molar absorptivity cannot be found in various of articles, it is also difficult to figure out since no complete calibration curve was given.
Tranexamic acid: according to the research, the tranexamic acid compound is unable to be directly analyzed by the UV-Vis since no chromophore is in the molecule.(1) However, the derivatization is a better choice, through a high yield and sensitive reaction to the original analyte, make it more sensitively to be seen by the UV-Vis system.
Three most important steps of the experiment are:
1. Find out a suitable derivatizing agent, conduct the reaction with the target analyte. (the reaction should be as complete as possible, the evaluation of the irreversibility and the sentivity of are important.)
2. Keep the derivatized product from light source, acids, bases and oxidizing agent in case of the conversion of the analyte's interest.
3. The need for internal standards should be evaluated improvement of the method. (4)
(1) Nycz, Jacek E.; Malecki, Grzegorz; Morag, Monika; Nowak, Gerard; Ponikiewski, Lukasz; Kusz, Joachim; Switlicka, Anna. "Arbutin: Isolation, X-ray structure and computational studies". Journal of molecular structures vol.980. 2010, (0022-2860)
(2)Shih, Ying; Wu, Kuan-Lin; Sue, Jun-Wei; Kumar, Annamalai Senthil; Zen, Jyh-Myng. "Determination of tranexamic acid in cosmetic products by high-performance liquid chromatography coupled with barrel plating nickel electrode" Journal of Pharmaceutical and Biomedical Analysis. (2008) 0731-7085
(3) "Microdialysis sampling coupled to on-line high-performance liquid chromatography for determination of arbutin in whitening cosmetics." Journal of chromatography. B. Vol.829. 2005(1570-0232)
(4) Beverly Nickerson. "Sample Preparation of Pharmaceutical Dosage Forms: Challenges and Strategies for Sample Preparation and Extraction". page 333. ISBN:9781441996305
SIMILAR ANALYTICAL PROBLEMS
My research project is similar to Melissa Eubanks' silicones in cosmetics, since we both focus on specific compound that added in the cosmetics and skincare products, the difference is , she concerns the silicione washedovers to the environment and my issue more concern about the human health. Another similar problem is Abdihakim Abdullahi's mercury in skin supplies, that we both want to analyze compounds in the skin whitening products, that we may have similar approach to determine the target ingredient in products.
Can be purchased at sigma-aldrich company, the product number is A4256. The sample has a purity higher than 98% and the price is $104.50 for 10g.
Can be purchased at sigma-aldrich company, the product number is 857653. The sample has a purity of 97% and the price is $41.50 for 10g
Atomic spectrometry is not useful to quantify the analytes , mass spectrometry may be used to determine the quantity of the analyte.
Analyte arbutin has a molecular weight of 272.25, the nominal molecular weight is 272.
Analyte tranexamic aicd has a molecular weight of 157.21, and the nominal molecular weight is 158.
Proper of ionization sources may be FD-TOF and ESI-trip Quad.
The mass spectrum(7) of tranexamic acid has its base peak at 122.7, and other peaks are at 95.1, 141.0 and 158.0. The spectrometry was LC-MS/MS, the spectrum was got by a sample which has a tranexamic acid concentration of 1E-4g/ml. The chromatohrapy was performed on surveyor liquid chromatography system, using a 5 micro hypurity C18 thermohypersil column (150*2.1mm i.d.) maintained at 20 oC.
The mass spectrum of arbutin was determined by a GC-MS spectrum(8), which is used very common in labs. The spectrum has its base peak at 73, however, the peak with is nominal molecular weight was not very high. The sample was prepared by diluted with DCM and injected 1micro liter in to the GC-MS system. The high purity helium was used as a carrier gas at 1ml/min flow rate. The oven temperature program was: from 120oC to 280oC in two minutes at a steady rate.
(7) Grassin Delyle, Stanislas. Clinica Chimica acta. 2010 Vol. 411 0009-8981
(8)Chisvert. A. Tanlata. 2010, Vol. 81. 0039-9140
Sample preparation of arbutin for GC/MS spectrometer. (9)
1. Sample was weighed out in proper amount, (0.01-0.02g), was weighed in a 10-ml volumetric flask.
2. Sample was dissolved in approximately 5ml of DMF (an ultrasonic water bath was used to facilitate the sample solving process).
3. The solution was then diluted to mark with the DMF to dilute the sample.
4. The solution was filtered with a 0.45µm nylon membrane filter.
Sample preparation of tranexamic acid for LC/MS-MS.(10)
1. 10ml of the internal standard solution (0.5g/L) was made and added into the 100µL sample which was contained into a 1.5mL plastic tube.
2. 100µL of perchloric acid(2.5% w/w) were than added.
3. sample was then vortex mixed for 30s and centrifuged at 14,000rpm for 10min.
4. 100µL of the aqueous supernatant was decanted into another tube and 150µL of sodium hydroxide (0.1M) was added.
5. sample was vortex mixed for 10s, and transferred into injection vials for analysis.
(9). Microdialysis sampling coupled to on-line high-performance liquid chromatography for determination of arbutin in whitening cosmetics. Journal of chromatography.B. 2005, vol.829, 1570-0232.
(10).Gaussin Delyle. S. , Chinica Chimica Acta., 2010. Vol. 411., 438-443
1. For my analytical problems, the gas chromatography, reverse phase chromatography, HILIC, affinity chromatography, chiral chromatography and size exclusion chromatography are suitable for analyze the compounds.
The Ion-Exchange chromatography is not suitable since there are no ions in my interested analytes.
2. I think the reverse phase chromatography is the most suitable technique to determine both analytes. Since both compounds are polar in structures, however, they each varied in the polarity substantially, the reversed phase chromatography is a good technique to separate.
3. The Nucleosil brand C18(11) (10µm,25*0.46cm) column was used for the separation, it is the medium density octadecyl , endcapped column, the structure of the stationary phase is "-(CH2)17-CH3". The PH stability of 20oC: 2-8, the number is 718966.
4. The mobile phase for the separation was acetonitrile/water (v:v 50:50), the PH of the mobile phase was adjusted to 2.6 by phosphoric acid (85%, w/w).(12)
5. The detector I am going to use is the UV-Vis detector, since both analytes are absorbed and emitted in the UV range.
(12): M. Saeed Arayne, Naima Sultana, Faiza Qureshi, Farhan Ahmed Siddiqui, Agha Zeeshan Mirza, Saima Sher Bahadur,Muhammad Hashim Zuberi., Chromatographia, 2009, Vol.70, 789-795
Both of arbutin and tranexamic acid are electroactive, thus the capillary electrophoresis method was able to determine and quantify the analytes in samples.
Instrumentation: it is performed using a CHI 821b electrochemical workstation. The reference electrode is Ag/AgCl , the platinum wire is as the auxiliary electrode. The detector is the UV-Vis detector.
Sample prepration: sample and MnO2 powder (particle size≤5 µm) are prepared and make into an aqueous solution with deionized water. The standard stock solution (10 000 ppm in 0.1M H3PO4) is going to be diluted by H3PO4 in different volumes to make different standard sample solutions.
To quantify the analytes in samples, it is useful to detect the current of each samples since the concentration of analytes is proportional to the currents.
(14)Jyh-Myng Zen, Hsueh-Hui Yang, Mei-Hsin Chiu, Chao-Hsun Yang, Ying Shin. Journal of AOAC International. Vol. 94, 2011, 985-990
Waste water sludge has shown to be a valuable lipid feedstock for the synthesis of Biodiesel fuel comprised of monoalkyl esters. This is due to the high cost of vegetable oils and animal fats relative to the cost of standard petroleum sources of diesel fuel. Biodiesel fuels made from waste water sludge are a %100 carbon neutral fuel source and as such represent an enormous step forward in the field of green chemistry.
The problem with the synthesis of this fuel lies in the purity of the lipidic material needed to perform the desired transesterification, and many methods have been proposed. These methods include cosolvents and shear mixing, but none show cost effectiveness. Even if a reasonable method is found to separate these fatty oils, a challenge lies in quickly and effectively characterizing the desired compounds, as the desired reactant that can be transesterified is very similar to the other lipidic material present in the waste water sludge. Certain methods of reaction, such as acid catalyzed transesterification, have been suggested, but these react very selectively with only a certain subset of lipid chains present in the sludge mixture. (1)
The analytes in this process are the lipidic material present and the biodiesel monoalkl ester that is desired. The matrix that these analyltes are found in includes the original filtered waste water feedstock and the final product stream that includes the biodiesel fuel. (1)
UV-Vis Absorption Spectroscopy
Because Diesel fuel is a mixture of saturated hydrocarbons and aromatic hydrocarbons, any analytical technique involving UV/VIS spectroscopy would likely yield spectra with far too many indistinguishable peaks. Like many analytical techniques, cost effective forms of UV/VIS spec requisite reasonably pure samples in order to distinguish individual compounds. Because of this, the raw form of this diesel fuel can not be identified or characterized using solely UV/VIS techniques. (1)
In order to make the mixture of paraffins and aromatics susceptible to UV/VIS, the individual compounds present in even a purified form of the diesel fuel must be isolated. This can be done effectively by separating the compounds by both mass and polarity. Roughly 25% of the diesel mixture classically consists of napthalenes and alkylbenzes and all of these should be separable through techniques such as GC or through column chromatography. (2) After these techniques are employed, it would be possible to characterize each individual portion of the fuel in order to determine both the composition and, to a certain extent, the purity of the compound.
The analytical issue lies determining the optimal purity and composition when balanced with the cost of performing seperative techniques on a large scale. As of now the analytical issue lies in determining how to separate the desired reactants/product from the waste water sludge. (1)
The hypothesis in this problem lies in determining how to best separate the final fuel from the FAME, Methanol, and other organic compounds present in the Matrix. The analyze in this case could be any of the components of diesel fuel, but the trouble lies in separating and then determining when the product is pure enough to be consumed as a transportation fuel.
Analyte Structure and Standard Purchasing Information
Shown here is the structure of FAME (fatty acid methyl esters) which can be seen as the largest component of most biodiesel fuels, as it is synthesized from fatty acid chains present in the wastewater sludge. Both analytes are shown here in the reaction scheme. These analytes being FAME and fatty acids and oils.
Image Citation: (1)
FAMEs can be purchased from http://fullgreenfood.en.alibaba.com/ with several different options for purity. This can be useful for determining how pure the final product analyte must be in order to be both analyzed and used as a fuel. The Oils and fatty acids that must be analyzed in both the product and reactant mixtures can be purchased from any company that sells standard cooking oils (1). Studies pertaining to the formation of FAMEs have explored similar methods. Otherwise, to use the intended wastewater sludge, this can be procured from any wastewater treatment plant.
Atomic and Mass Spectroscopies
Atomic Spectroscopies are unsuitable to accurately detect the analytes for this problem. Both analytes are relatively large molecules (FAMEs are roughly 280-350 Da and oils and fatty acids are roughly 600-1000 Da) with a large range of masses that are present. Its likely that any absorption or emission spectroscopy would likely be too imprecise because of the large number of varying molecular weights present in a realistic matrix. (3) Because of this, Mass Spectroscopy would be a better fit.
The best method of ionization would be ESI. This is due to it being a soft ionization technique, which works well for larger molecules without risking destroying the relatively sensitive structure of large fatty acids. The best type of selection and detection is likely a linear quadrupole ion trap analyzed using FT-ICR. The large molecules that make up the matrix would be easily separated by a linear ion trap. FT-ICR would simply make quick analysis quicker and easier, as many trials of various reaction conditions would be run. (4)
Sample Preparation Procedures
Because the stock samples needed for analysis in this case can be purchased in pure forms, separation for analysis is not necessary when preparing from stock solutions. However, separating analytes both before and after the trans-esterification is important for analysis and fuel purity. The separative technique for mass producing the biofuel suggested in studies has been shear mixing and phase separation in methanol (1). For analysis:
1. Liquid Phase separation in Ethyl Ether or Ethyl Acetate would work well, followed by a brine wash to dry the solution as much as possible would likely be effective (1).
2. Evaporation of the solvent may be necessary depending on the analytical technique being employed. If GC/MS is used this my not be needed. However, for H1NMR analysis or IR analysis is may be necessary to concentrated the analytes.
This technique may be used for analysis both before and after the reaction takes place.
HILIC, Reverse Phase, Normal Phase, Ion-exchange, and Gas Chromatography would all be acceptable for separating and analyzes both sets of analytes for this particular problem. Size-Exclusion, Affinity, and Chiral Chromatography are not applicable here. Size- Exclusion Chromatography would not be useful as it the hydrocarbon analytes are mixtures of many hydrocarbons ranging from C8 to C18 and the FAME products are mixtures of many different types of hydrocarbons, all of which can be seen as a 'FAME' type fuel. The issues with this type of chromatography is that it will not give detailed information on the concentrations of the useful analytes, as it can not tell them apart. (2) Affinity Chromatography simply doe not apply. Chiral Chromatography is also not useful as the analyte chirality is not an issue that affects the formation of FAMEs or the way in which this biofuel combusts (1).
The most useful seperative technique would likely be HILIC, as the hydrophilic and hydrophobic interactions of the individual hydrocarbons would easily separate different weight lipids, including FAMEs from the matrix mixture and give clear data on the different compositions of the product and reactant mixtures. (5)
A useful column for this separation can be purchased from ES Industries. The column is stainless steel, is 5cm in length, and 0.75mm in diameter. The Particles size is 1.8u and the diameter is 120A. The stationary phase of the column is silica gel designed for HILIC separation. The column can be purchased at http://esind.com/pages/products/products_02_2.tpl.
The mobile phase for HILIC would likely be a mixture of acetonitrile or THF and water. For the given analytes, acetonitrile would likely be a better choice as it would separate the composition of the analyze more effectively. (5)
The detector for this type of separation would like be some type of Mass Spectrometer, as mentioned in a previous blog posting. MS would give the clearest data for the separation and be able to analyze each component as it eluted from the column. While the technique may be arduous to analyze, it would be the most effective way to determine the exact composition of the lipidic material reactant and the FAME product.
Preferred Analytical Technique
The preferred technique for the analysis of lipidic material present in waste water treatment plants and FAMEs (the biodiesel fuel that can be synthesized from said lipids) would be HILIC chromatography using Mass Spectroscopy as a detector for. The lipidic material would need to be extracted, via liquid phase extraction, and then concentrated in order to undergo proper analysis using HILIC. The FAME material would best be analyzed after it is filtered and distilled from the reaction media. It is essential that the FAME material be analyzed in its final fuel form, as the composition of this biofuel is the crucial information needed to solve this analytical problem.
The analytical problem which uses the most similar analytical technique as mine would be Andrew Szeliga's problem of Perflourooctonoic acid in human blood. Both techniques involve a chromatographic column followed by mass spectroscopy as the detector. The analyte is also similarly complex and will require similar a similar type of seperatory technique in order to use the specified analytical technique.
Capillary Electrophoresis Techniques
For the FAMEs and lipids present in the reactant and product analytes, standard CE would likely not be effective, as ll of these products are similarly uncharged and present very little charge. For this reason, MEKC would likely work well, as the compounds do show differenced in hydrophobicity. SDS would work well as the surfactant buffer, with water as the mobil phase. For this any MEKC coated capillary would work.
As with other analytical techniques, using MS as a detector would likely work best, considering it would provide the most accurate and distinct information based on the analytes.
(1) Karbo, D. M. Biodiesel Production from Municipal Fuel Sludges. Energy and Fuels. [Online] 2010. http://pubs.acs.org/doi/pdf/10.1021/ef1001106 (accessed September 12th, 2011).
(2) Agency for Toxic Substances and Disease Registry, Center for Disease Control. Toxicology Profiles for Fuel Sources. http://www.atsdr.cdc.gov/toxprofiles/tp75-c3.pdf.
(3) Radziszewski, J.G.; et. al. Infrared Absorbtion Spectroscopy of the Phenyl Biradical. J. Am. Chem. Soc. 1996, 118 (31), pp 7400-7401.
(4) McLafferty, F.W.; et. al. Tandem Fourier Transform Mass Spectroscopy of Large Molecules. Fourier Transform Mass Spectroscopy. [Online] 1987, 7, 116-126 http://pubs.acs.org/doi/abs/10.1021/bk-1987-0359.ch007 (accessed October 25th, 2011).
(5) Alpert, J.A. Hydrophilic-interaction chromatography for the separation of peptides, nucleic acids and other polar compounds. Journal of Chromatography A. 1990, 499, pp 177-196.
Performance enhancing supplement is a multibillion dollar industry and is endorsed by bodybuilders from all around the world. Surprisingly, the majority of these sport supplements, which are being sold at your local nutritional stores, are not regulated by the FDA. The topic of interest is the nitric oxide (NO) compound in sport supplements. NO is relatively new in bodybuilding supplementation and not much is known about its correlation with muscle growth. Brands such as N.O.-Xplode 2.0TM, SuperPump250 TM, NO Beta TM, Epozine-02 NT TM, etc..., have all claimed an increase in muscle pump or muscle density from the use of NO. The synthesis of NO is simple and natural in the human body. NO can be obtained from L-arginine, which one could obtain from eating chicken. The amount of L-arginine consumed by humans per day is less than 1g. More research is needed to determine the conversion factor from L-arginine to NO. Surprisingly, the best selling NO product does not list the amount of L-arginine, but it does contain approximately 19.6g of NO. In the body, NO is synthesized by the nitric oxide synthase, a complex enzyme, which reacts with oxygen, L-arginine, and NADPH to produce NO, citrulline, and NADP+. NO in vivo has a very short half life and undergoes reactions with other biological molecules in the blood fluid to create, for example, NO3- and NO2-. Therefore, the nitrate/nitrate ratio would give the best indication of NO production.
During exercise, the blood vessels dilate naturally due to the usage of ATP and the production of metabolic byproduct. Also, an in increase blood vessel diameter also allows an increase in blood flow and oxygen to the needed muscles. The maximum dilation of the blood vessel in a normal human needs further research. One question to ask is if the blood vessel is expanded to the max during a regular workout, would excess NO be needed? Because of the principle of increase blood and oxygen flow during vasodilation, nutritional supplement manufactures claim that the added NO in powders would add to the effect of vasodilation and increase muscle density. The role of NO itself to increase muscle density is not known, however, NO is known to work with other molecules that are also provided with the product such as the essential amino acids, microfractions, alpha-lactalbumin, beta-lactoglobulin, glutamine, glutamine precursors, etc, etc, etc... (whatever they want to print on the label), to increase muscle density. One molecule that is proven to increase power and muscle mass in proper resistance training is whey isolate protein. Whey isolate protein is a more purified form of whey protein which is also costly. A brand, for example, that has no NO but has whey isolate protein is the Gold Standard Whey TM. It is proven that NO is a vasodilator, play an important in neurotransmission, and is a precursor to photochemical smog (2), but the claim that NO itself has a correlation with increased muscle density is just a hype and is used to increase the market price of the product.
The central hypothesis in this study is that NO does not promote muscle growth. There are two major parts to testing this hypothesis. The first part is analyzing the amount of NO in blood. This could be done by taking the plasma nitrate/nitrite and performing nitrate reductase to convert it into nitrite. In the nitrite form, Griess reaction could be applied to turn it into a deep purple azo color where the nitrite composition could be determined with UV-Vis absorption spectrometry at about 540-550nm. The chemical compound responsible for the color is the azo structure. The solvents that could be used include Milli-Q water or the provided Assay Buffer from the colorimetric assay kit (item No. 780001). The analytes of interest is the plasma nitrate/nitrate and the matrix includes all of the other components found in blood including the unwanted byproducts in the Griess Reaction (3).
Similar Analytical Problem
The analytical problems similar to mine are of Matthew Marah and Andrew Szeliga because our analytical problems deal with a blood matrix. Andrew Szeliga's topic is about perfluoroocatanoic acid levels in human blood. His hypothesis is that people who have close exposure to sources of PFOA dumping will exhibit elevated levels of PFOA in their bloodstream. The matrix would be the blood and the relevance of the study is of health concerns. Matthew Marah's topic is about Cadmium levels in people. His central hypothesis is that people who live close to plants (ie. Industrial plants) will have higher levels of Cd in their blood. The matrix would also be the blood and the relevance of this study is also of health concerns. These are similar to my analytical problem because the matrix is the blood. However, it is also different because our analyte is different. The absorption ranges for each analyte are different. Moreover, pure Cd doesn't seem to have a UV-Vis range. If an oxidized form of Cd, for example, gives the best indication of Cd in the blood, it would be very similar to my testing procedure because I would be using nitrate/nitrite as an indicator for NO due to NO's biological reactions in vivo.
(1) Allen, Jason, and J D DAllen. "Nitrite, NO and hypoxic vasodilation." British Journal of Pharmacology 158.7 (2009):1653.
(2) Nyberg, Michael, and MNyberg. "Interstitial and Plasma Adenosine Stimulate Nitric Oxide and Prostacyclin Formation in Human Skeletal Muscle." Hypertension 56.6 (2010):1102.
(3) J, Bloomer, and Bloomer Richard J. "Acute effect of nitric oxide supplement on blood nitrate/nitrite and hemodynamic variables in resistance trained men." Journal of Strength and Conditioning Research 24.10 (2010):2587.
Chemical stricture and standards
The three chemical reactions below represent the production of the analyte of interest:
NO + O_2^- →ONO_2^- + H_^+ →NO_3^- + H_^+
2NO + O_2^ →N_2 O_4 + H2O →NO_2^- + NO_3^-
NO + NO_2^ →N_2 O_3 + H2O →〖2NO〗_2^-
Because NO is highly reactive with other biological fluids in vivo, the sum of NO_2^- and NO_3^- concentrations would be the best representation of NO production. In this example, the possible analytes will all be converted to nitrite via nitrate reductase which will then be reacted with Griess reagent to produce the desired azo product. The chemical structure shown below illustrates the product after nitrate reductase, which is a representation of the analyte of interest before the Griess reagent reaction. Otherwise, the analytes of interest are simply NO, NO_2^- and NO_3^-.
At a cost of $185.00, Cayman Chemical Company, located in Ann Arbor Michigan, can provide a Nitrate/Nitrite Colorimetric Assay Kit (item No. 780001) that contains standards, 1 vial per standard, for both nitrate (item No. 780014) and nitrite (item No. 780016) for the construction of calibration curves. The catalog No. is 760871.
"Nitrate/Nitrite Colorimetric Assay Kit." Cayman Chemical. 30 March 2011. Web. 23 October 2011.
Mass spec of NO
1. From class lectures and scholarly journals, the type of chromatography that is best suited for my analytical problem is a high performance anion exchange chromatography. One could use a GC-MS-validated anion-paring HPLC with ultraviolet absorbance detection at 205 nm, however, this method is not suitable to measure nitrate in human plasma. One could use HPIC do determine nitric oxide in human plasma however large amounts of Cl ions would result in poor peak resolution. HPLC, CE or other MS-based techniques are also suitable methods for the analysis of nitrite and nitrate in human biological fluids, however, high performance anion exchange chromatography would be most suitable.
2. High performance anion exchange chromatography (HPAE) would be my first choice because this technique is rapid, very sensitive, and has an accurate method with a LOD for nitrate of 0.1 microM/L. It doesn't require much precolumn derivatization and that nitric oxide, nitrate, and nitrite can be measured directly. It was also found to be suited for analyzing and separating nitric oxide and nitric oxide derivatives in human biological fluids.
3. A commercial column that is available is the Sphereclone column provided by Phenomenex. The column that would be used would be a 250 x 4.6 mm, Sphereclone column with a 5 micro SAX stationary phase with an anion exchanger (SEM based silica). The stationary phase would be comprised of SAX and has a fully porous silica as a solid support with a pore size of 80 angstrom. The composition of the mobile phase that would be used is 5mM k^-2HPO^-4 and 25MM KH^-2PO^-4, with a pH of 3.0. The mobile phase would be pumped at 1.5 ml/min and the effluent would be monitored at 214nm. The injection volume would be at 20 microL and the column could be kept at 35 degrees C and the samples could be kept at 4 degrees C. The part number is 00G-4149-E0.
4. The composition of the mobile phase that would be used is 5mM k^-2HPO^-4 and 25MM KH^-2PO^-4, with a pH of 3.0. The mobile phase would be pumped at 1.5 ml/min.
5. The recommended detector would be the UV-VIS detector SPD 10 AV. This detector would be practical because it has a high visible sensitivity, high scanning speed, and has low noise. The cell volume for this detector is 12 microL and at 210nm, one would have to use the deuterium lamp (190 - 370nm).
Sharma, Arun et al. "Determination of nitric oxide metabolites, nitrate and nitrite, in Anopheles culicifacies mosquito midgut and haemolymph by anion exchange high-performance liquid chromatography: plausible mechanism of refractoriness." Malaria Journal 7 (2008) : 71.
Phenomenex. 2010. 10 November 2011.
Specification Sheet SPD-20A/SPD-20AV. 2006. 10 November 2011.
Capillary electrophoresis techniques
1. Out of CZE, MEKC, cIEF, or CGE, CZE would be most suitable to separate my analytes from other matrix components. MEKC would not be applicable because we are not interested in separating uncharged species despite that MEKC also separates charged species. Nitric oxide is not an amphiprotic specie, therefore cIEF would not be useful. CGE is useful for larger, macromolecules and would not be suitable because NO is a small molecule. However, from lecture 30, microchip-CE would be the most adequate technique for separating NO from biological matrices.
2. Microchip-CE would be my first choice because only a small sample is required, it has a high sample throughput, and has a high sensitivity with a UV-Vis detector. My second choice would be CZE because it is good for small anionic separation, has high resolution, it is cost efficient, and has a high sample throughput.
3. For the MCE, an artificial serum (Na2HPO4, NaHCO3, KCl, NaCl, sodium lactate, urea, glucose, sodium sulfate) would be prepared to a pH of 7.4 and the running buffer (same composition) would also be prepared to a pH of 7.4 with 0.1M HCL. The voltage that would be used would be 0.15kV because this was found to be the optimal voltage from Miyado's study (1). Because the separation channel in the microchip that would be used is short (Type-U, 35mm x 12mm with 50um wide x 20um deep), one can operate without an EOF modifier. This would allow the sample ions to flow against the EOF, lengthening the separation channel. A slightly higher injection volume would then be required to fix low sensitivity and resolution.
For CZE, buffer would include arginine, borate and TTAOH with tetradecytrimethyl-ammonium hydroxide modifying solution. Alkaline species for buffer solutions would be used because it would induce the formation of charged coupled binary layers with the inner surface of the fused silica capillary tube. The pH would be adjusted to 9.5 via 1M NaOH and the running buffer would be operated at -20kV. In both the MCE and CZE, a sample injector with pressure would be used as a sample loading method.
4. I would be using a UV-Vis detector for both methods. For the MCE, I would be using a UV-Vis detector at 214nm with a linear photodiode array detector because nitric oxide fluoresce well. For CZE, I would use a conductivity detector to detect UV because it is 10-folds better in LOD compared to UV-light-based detection. However, in both methods, the only difficulty is that it is not easy to analyze anions in biological fluids.
(1) Miyado, Takashi, TMIYADO, andMiyado. "High-throughput nitric oxide assay in biological fluids using microchip capillary electrophoresis." Journal of chromatography 1109.2 (2006):174.
(2) Y, B o u d k o, andBoudko Dmitri Y. "High-resolution capillary electrophoresis of nitrite and nitrate in biological samples." Methods in molecular biology 279(2004):9.
1. Yes nitric oxide is electroactive
2. With electrochemistry, selective electrodes could be used to identify nitric oxide. Materials to construct the working electrode could include platinum, carbon fiber, glassy carbon, or gold. Akin to other cases, there would always be interfering species and in this case, for example, interference from gaseous oxygen would be a concern if nitric oxide is being measured by means of electroreduction. To identify nitric oxide, interfering species could be reduced by the type of sensor, applied potential, characteristics of the permselective membrane and the biological location. From (1), a bare Pt microelectrode modified with Ni tetrasulfonated phthalocyanine could be used in situ, however, this would involve the electrode to be within the human for in situ analysis.
3. The size of the electrode and the distance at which it is measuring the source of nitric oxide affects NO quantification in biological systems. From the study of (1), it was found that larger working electrodes have larger NO sensitivity and that the NO concentration would decay rapidly as the distance increased from the NO source. Because my analytes are in blood, a larger electrode would be used for bulk NO measurement.
(1) Privett, Benjamin, and B J JPrivett. "Electrochemical nitric oxide sensors for physiological measurements." Chemical Society reviews 39.6 (2010):1925.
The recent disaster at the Fukushima Daiichhi nuclear power plant released many radionuclides into surrounding area. One of the main concerns after the evacuation of the area was radiation contamination of the area's food supply. Milk from Japan has shown higher levels of radioactive I-131 than is allowed by law. The FDA has even banned food products from Japan including milk. How can I-131 be detected in milk and the radiation levels quantified in as quick and accurate manner as possible? This is an important problem to solve because radiation levels for the public should always be kept as low as possible. More specifically I-131 can cause thyroid cancer especially in infants and young children. The central hypothesis is that I-131 in milk will have higher radiation levels closer to the nuclear plant. The analyte is I-131 in milk and the matrix is the milk and any contaminates in it.
Wakeford, Richard. And now, Fukushima. Journal of Radiological Protection [Online] 2011, 31, 167-176 http://iopscience.iop.org/0952-4746/31/2/E02/ (accessed Sept. 20, 2011)
Lubick, Naomi. Little Radioactive Material From Fukushima Reached Europe. Chemical and Engineering News [Online] 2011 http://pubs.acs.org/isubscribe/journals/cen/89/i34/html/8934scene.html (accessed Sept. 20, 2011)
UV Vis Absorption Spectrum
5b. I-131 won't absorb in UV-Vis spectrum but Iodide will react with starch, specifically amylose, to give a blue amylose-iodide complex. This method has been used but it seems that it is normally used to find the concentration of amylose as opposed to iodide. The iodide has a complex equilibrium with I(2) and I(3)- based on its concentration in the solvent. Ideally the equilibrium would be pushed all the way to 100% I(3)- because that is the species that forms a complex with amylose. This will not be a easy and straightforward way to find I concentration but it should work. Also I do not think this method will differentiate between I-131 and any other isotope so it would only really confirm the presence of Iodide in milk sample
1. dissolve amylose in 90% dimethyl sulfoxide and 10%water
2. isolate I-131 from milk samples
3. add I-131 and dilute to 10% dimthyl sulfoxide and blue amylose-iodide complex forms
maximum wavelength: 600nm with dimethyl sulfoxide
molar absorptivity: varies based on solvent concentration but mean value is 26,119(L/mol*cm)
Question 3 was originally searched for using CHEM 4101 library page. There weren't any promising papers and I wasn't expecting to find uv-vis info regarding I-131 so I modified search to looking for starch-iodide uv-vis information.
Knutson, C.A. A Simplified Colorimetric Procedure for Determination of Amylose in Maize Starch. Cereal Chemistry. 1985, 63, 89-92.
Similar Analytical Problems
a.Justin Michael- Boron in Groundwater
He is concerned with figuring out how to best remove boron from the environment using different sorbents to reach standard limits for drinking water. The analyte is boron, matrix is groundwater samples so likely very complex. Relevant because both are concerned with quantifying an element that is potentially harmful to people.
Osman Janshed- Detecting Prions
He is concerned with detection of prions in food before people eat them. The analyte is prions in a matrix of meat. It might be a little stretch to say they are similar but we discussed that we may have similar matrix with them both being food products.
b. Boron could have a similar study as I will need to do a study of I-131 concentrations based on distance. Boron may find this useful to see how groundwater treated in one place effects groundwater in nearby areas. Also for me studies might be useful to collect data on how cows are housed(inside/outside), food storage(inside/outside), milk processing(I-131 in large milk collection tanks, etc...). negative control for myself could be done in similar parts of Japan that have not been affected by Fukushima, any historical data of this sort for Japan.
c. My studies will probably not be similar to Osman's because our similarity is with the matrix. The studies listed above besides by distance will be unique to only my analytical problem.
Blog 6 Chemical Structures
I have not been able to find a definitive form of I-131 in milk but I know I2 is a stable and common form of Iodine. In studies quantifying iodine concentrations in milk they do not specifically say what from it is in. As far as detecting I-131 with a geiger meter the form of I-131 is irrelevant since no sample prep is needed for this type of detection.
Perkin Elmer sells radiochemicals including I-131. The catalog number for the most active sample is NEZ035A025MC which is 25mCi of NaI-131 in NaOH. The price isn't listed on the website.
Dahl, L;Opsahl, J; Meltzer, H; Julshamm, K. Iodine concentration in Norwegian milk and dairy products. British Journal of Nutrition 2003 90, 679-685
I want to explore whether the silicone, commonly referred to as cyclomethicone, used in cosmetic products is harming the marine environment. Originally methylcyclotetrasiloxane, aka D4, was used in cosmetics but it was found that it was washing off skin and hair and building up the marine environment. So decamethylcyclopentasiloxane, aka D5, replaced D4 in cosmetics. Decamethylcyclopentasiloxane is a volatile that is released to the atmosphere in large quantities (2). There are also concerns that D5 is accumulating in the marine environment.
This is an important issue because D5 is used in many cosmetic products and is just being washed down the drain, it is not toxic to humans but it is possible that its harming the marine environment (1). There are other alternatives to using D5 but manufactures of the cosmetics are concerned that their products won't give consumers the same results without the D5 and that their profits would decline.
The hypothesis is that D5 is harming marine environment because it is accumulating, and even in its purified form there are residual levels of D4, that are harming marine organisms (1).
The main analyte to be focused on is decamethylcyclopentasiloxane but methylcyclotetrasiloxane will also be looked at to determine if there are toxic levels of D4 present in D5. The matrix where D5 could be found is the water where a lot of drain water is deposited without treatment, as well as marine organisms.
1). Reisch, M. Storm Over Silicones. C&EN Northeast News Bureau 2011, 89, pp 10-13.
2). McLachlan, M.; Kierkegaard, A.; Hansen, K.; Van Egmond, R.; Christensen, J.; Skjøth, C. Concentrations and Fate of Decamethylcyclopentasiloxane (D5) in the Atmosphere. Environ. Sci. Technol 2010, 44 (14), pp 5365-5370.
UV-Vis absorption spectrometry
I could not find any articles defining the maximum wavelengths of absorption for decamethylcyclopentasiloxane. I do not believe that it has a UV-vis range and I could only find information about the use of NMR, IR, Mass Spec, and GC for the determination of D5.
Similar Analytical Problem:
Chuxin Chen's analytical problem is the comparative analysis of arbutin and tranexamic acid in skin whitening products. The hypothesis is tranexamic acid has better performance in skin whitening and more reliable to use externally. This analytical problem is relevant because the use of skin whitening creams is increasing and there seems to be a difference in price and effectiveness of the product according to which compound it contains. The analytical problem is similar to my problem in that we are both targeting a specific compound found in cosmetics and personal care products. Both analytical problems are concerned with the health risks but mine focuses on the environmental aspect while Chuxin's problem focuses on the use of the skin whitening products by humans and those risks. The matrices are different; Chuxin will be looking at the skin creams, while I'll be targeting the sediment and aquatic life to find the concentration of D5.
Hypothesis:Decamethylcyclopentasiloxane is washing off skin when used in cosmetic products and accumulating in the aquatic life.
Studies: (A) Identify regions that contain D5 and/or water treatment plants that are not taking D5 out of the water. Determine if there is a difference in levels of D5 in fish and sediment correlating to the distance from the source of D5. (B) Measure the concentration of D5 in water found to contain D5. (C) Based on concentrations found in the water, do a study to see if there is a higher concentration of D5 in the fish and sediment, therefore showing an accumulation.
Alternative Studies: If there is not a high concentration of D5 in the water and aquatic life, then determine concentration in air because D5 is a volatile cyclic methylsiloxane.
The concentration of D5 found in sediment ranged between 60-260 ng/g (d.w.). The concentration of D5 in ragworms was 51-760 ng/g (McLachlan).
McLachlan, M.; Kierkegaard, A.; Hansen, K.; Van Egmond, R.; Christensen, J.; Skjøth, C. Concentrations and Fate of Decamethylcyclopentasiloxane (D5) in the Atmosphere. Environ. Sci. Technol 2010, 44 (14), pp 5365-5370.
BLOG 5: Fluorescence
D5 is not fluorescent; it does not have a rigid structure, which is favored by fluorescence. Fluorescence is found in compounds that have aromatic functional groups with low energy pi-pi transitions and D5 does not contain aromatic compounds. D5 can be observed using infrared spectrometry, and a range of bands can be seen from 1264-808cm-1. A strong band can be seen at 1263cm-1 while a peak correlating to the SiO species can be found at 1224cm-1 (Almond).
Almond, M. Becerra, R. Bowes, S. Cannady, J. Ogden, S. Young, N and Walsh R. A Mechanistic Study of the Low Pressure Pyrolysis of Linear Siloxanes. Physical Chemistry Chemical Physics. 2008, 11, 6856-6861.
Decamethylcyclopentasiloxane, Single-Component Organic Standards can be purchased online from SPEX CertiPrep2
Catalog Number: S1110
1mL for $26
Nominal Mass: 370
Exact Mass: 370.773
Two Types of Mass Analyzers that can be used to Quantify D5:
Electron Impact Ionization- TOF2
This is a mass spec of D5 using Electron Impact Ionization and Time of Flight mass analyzer.
Gas-liquid chromatography mass spectrometry was carried out on the polymerisation reaction mixture using an AE1 MS-902 double focusing mass spectrometer. Column conditions: 3 ft x in. 0.d. glass column; 23 % OV-17 on Chromasorb G; column temperature programmed from 60 to 260 "C at 6 "C/min; 50 ml/min Helium carrier gas. Mass spectra were obtained with electron energies of 70 eV; accelerating potential, 8 kV; trap current, 100 PA; source temperature, 250 "C.
1.) Dong, X.; Proctor, A. Characterization of Poly(dimethylsiloxane)s by Time-of-Flight Secondary Ion Mass Spectrometry. Macromolecules, 1997, 30, 63-70.
2.) Pickering, G.; Oliff, C.; Rutt, K., The Mass Spectrometric Behaviour of Dimethylcyclosiloxanes. Organic Mass Spectrometry. 1975, 10, 1035-1045.
Food allergies are a serious medical concern for some people and a mere annoyance to others. Unfortunately, food allergies, particularly those to fruits and vegetables, can be a side effect of another common allergy: seasonal pollen allergies, or hay fever. This condition is called oral allergy syndrome, in which the body reacts to proteins in fruits and vegetables in the same way it can react to pollen, causing an allergic reaction (1). Fortunately, the type of pollen allergy a person has can determine what kind of fruits and vegetables they're allergic to. As someone who suffers from this, this is an important issue to me. The allergic reactions I've experienced to fruits have gotten steadily worse over time, starting as just watery eyes while eating an apple about 7 years ago to having my lips swell up for over a day after eating a peach last week. I personally do not want to accidentally ingest a fruit that I am allergic to and have my throat close on me. Consequently, one thing that concerns me is how genetics can affect the fruit's proteins. Genetically altered foods are showing up on the market now (2), but how do these foods differ from "natural" or organic foods? Are there any different proteins? Are the allergen proteins even there?
My hypothesis is that any minor genetic altering of a plant will not affect the proteins that cause the allergic reactions. A conclusion can be reached by analyzing fruit samples of genetically altered fruits, "organic" fruits, and fruits that are neither genetically altered or "organic." The analyte could be a variety of things. For example, one could test the skin of the fruit for protein content as well as juices from the meat of the fruit. The matrix of the juice would also contain carbohydrates and other organic molecules.
1. Mayo Clinic. Food Allergy: Symptoms. http://www.mayoclinic.com/health/food-allergy/DS00082/DSECTION=symptoms
2. Harry A. Kuiper, Gijs A. Kleter, Hub P. J. M. Noteborn, Esther J. Kok. Assessment of the food safety issues related to genetically modified foods. The Plant Journal 2001, vol. 27, issue 6, p. 503-528.
UV-Vis Absorption Spectrometry
With fruit allergies stemming from oral allergy syndrome, different proteins in different fruits can trigger reactions. Also, the proteins allergic reactions will result from are due to an individual's allergy to a specific kind of pollen. Consequently, the wavelengths and extinction coefficient depend on which allergy and protein one is analyzing. For example, the proteins Art v 1 and Act c 1 are the proteins in kiwi that cause allergic reactions due to complications from mugwort pollen allergies. In order to determine the concentration of these proteins, HPLC-UV is used, analyzing the separated proteins at 280 nm. The solvent used in analysis for Art v 1 and Act c 1 were acetate and NaCl, and Tris and citrate, respectively.
In the analysis of allergen content of the kiwi and mugwort samples, the extinction coefficients used were found to me 0.59 +/- 0.06 for Art v 1 and 1.72 +/- 0.02 for Act c 1.
As stated earlier, the values for both the absorption and the extinction coefficient should differ, depending on which allergy and protein are being examined.
2. Milan Blanusa, Iva Perovic, Milica Popovic, Natalija Polovic, Lidija Burazer, Mina Milovanovic, Marija Gavrovic-Jankulovic, Ratko Jankov, Tanja Cirkovic Velickovic. Quantification of Art v 1 and Act c 1 being major allergens of mugwort pollen and kiwi fruit extracts in mass-units by ion-exchange HPLC-UV method. Journal of Chromatography B 2007, vol. 857, issue 2, p. 188-194.
Blog 6: Chemical Structure and Standards
2. For the mal d 1 protein, the amino acid sequence is (1):
3. I was unable to find a company that sells the mal d 1 protein, or the mal d 2,3, and 4 proteins as well. However, the proteins can be extracted from an apple and purified (2). The concentration could be calculated by using Beer's law and a spectrometer (as mentioned in a previous entry) if the extinction coefficient is known.
1. All four electrophoresis methods seem like they would work just fine.
2. CGE seems like it would be the best choice. Although I could not find an example where the mal d proteins were analyzed via a CE method, CGE was used as a means to analyze the concentrations of other proteins in apples.
3. Since I was not able to find information directly on the mal d proteins, the following information is based off other proteins found in apples (proteins analyzed not known):
A coated fused-silica capillary is used with an internal diameter of 100um and a total length of 32.5 cm. TRIS, aspartic acid, SDS, and acrylamide were used as the buffer (pH 8). The voltage was 7kV, and the separation took less than 15 minutes. (1)
4. In the above example, they used a UV-vis spectrometer with two wavelengths analyzed (215 and 280). They had very low concentrations of analyte in the end (20 ug/ml). Although this would probably work for my problem, I think using a fluorimeter might be a better choice since fluorimeters are more sensitive, especially since the analyte concentration is so low. Also, the fluorescence excitation and emission wavelengths are known for my analyte.
1. Blanco Gomiz, Domingo et all., Size-based separations of proteins by capillary
electrophoresis using linear polyacrylamide as a sieving medium: Model studies and analysis of cider proteins. Electrophoresis, vol 24, issue 9, pg. 1391-1396.
The focus of my analytical problem is the presence of residual pesticides, or natural toxins in natural flavors and fragrances. The raw materials for natural flavors and perfumes are frequently sourced from fruits, spices, herbs, flowers, microbial fermentation and a number of other agricultural sources (1). Extraction is commonly done via steam distillation, expression, tincturing, distillation, and a number solvent extraction techniques. These are then commonly concentrated for a number of reasons, including added stability and ease of transportation (1). Any toxins, pesticides compounds present would also be concentrated, which would eventually reach the consumer (3). Produce is generally cleaned and treated before the fragrance or flavor is extracted but treatments are kept mild to preserve the character of the raw material. Another aspect to this is flavor and fragrance companies sourcing rare and unique raw materials from remote and undeveloped countries that may have sup-par quality control measures, accidental inclusion of heavy metals from groundwater, or use of banned pesticides still remain and issue. Part of my interest in this topic is consumer perception that "naturally" flavored products are healthier than artificial flavors.
The hypothesis is that these toxins and pesticides are concentrated in the raw materials for naturally flavors and fragrances. These could have an acute or chronic health impact on human health. Additional financial impact could stem from levels of contaminants below a level that could pose harm to the consumer.
Target analytes include common pesticides, naturally produced plant toxins, heavy metals.
These matrixes will commonly be alcohol, powdered, in oil emulsions, and occasionally in water. Matrices will be complex, and methodology will require high throughput, high sensitivity, and rapid multi-residue detection for application (2).
(1) Reineccius, Gary. Flavor Chemistry and Technology. Boca Raton : Taylor & Francis, c2006.
(2) Seiber, J N. "Contributions of Pesticide Residue Chemistry to Improving Food and Environmental Safety: Past and Present Accomplishments and Future Challenges." Journal of agricultural and food chemistry 59.14 (2011):7536-7543.
(3) Culliney, T W. "Pesticides and natural toxicants in foods." Agriculture, ecosystems & environment 41.3-4 (1992):297-320.
UV-Vis Absorption Spectrometry-
Driss et al (1993) has shown application of UV-Vis absorption in water at a wavelength of 254 nm in water, for simultaneous detection of parathion-methyl, parathion, fenitrothion, diazinon, azinphos-methyl, azinphos methyl, phosmet, carbaryl. Additionally another study reported detection of a mixture of seven insecticides using a wave length of 220 nm in a 80:20 or 70:30 methanol to water solution (Farran, 1988). A wave length of 290 nm was selected by Sultatos et al, however in this publication they did note that the maximum variation of each compound did vary somewhat, their detection included: Parathion, Paraxon, p-Nitrophenol, Chlorpyrifos, Chlorpyrifos Oxon, Trichloro-2-pyridinol, Methyl Chlorpyrifos, Methyl Chlorpyrifos Oxon, Azinphos Methyl, Coumaphos. Two of these papers also took time to analyze the oxon form of these toxins as oxons are converted into compounds with higher toxicity, and fat solubility in the human liver than their native form (Davies, 1975). All three of these methods use a separation method before detection, in many methods this is either gas or liquid chromatography. The structural differences between the various pesticides is limited and as such distinction between them using UV-Vis without a separation technique would be extremely challenging, if not impossible.
Molar absorptivity has been a challenge to find for all potentially applied pesticides, however research has been done to investigate molar absorptivity on some organophosphates, and some chloroacetanilides. These include: ε = 466 ± 41 for alachlor, ε = 3558 ± 323 for diazinon, ε = 5.5 ± 0.5 for dichlorvos, in units M-1cm-1 (Feigenbrugel, 2005). Although some literature values were identified, extensive literature was not found relating to the molar absorptivity of potential contaminants, this could stem from the application of mass spectroscopy for complex food matrices, do note this is speculative.
With identified analytes UV-vis absorption is expected, especially considering many of the organophosphates have a phenolic ring, or a nitrogen containing ring such as pyridine, pyrazine, pyrimidine. These compounds alone can be detected using UV-Vis spectroscopy, and additional ring substitutions would most likely enhance the likelihood of detection.
Please see comment on fruit proteins allergen post.
BLOG 6. Chemical structure and standards
Analytical Standard Sources-
Atrazine-Fluka 99% Pure- 250mg for $35.20. Product # 45330
Alachlor- Fluka 99% Pure- 250 mg for $20.70. Product # 45316 (C13 labeled 10mg for $282.50, #34086)
Diazinon- Fluka 99% Pure- 250 mg for $30.90. Product# 45428 (Deterium- 10mg for $691.10, Fluka Product# 492175)
Warfarin- Fluka 99% Pure- 250 mg for $34.50. Product#45706
Standard Preparation- Prepare samples through dilution of sample to analytical range. Using equally spaced concentrations prepared through serial dilution, analyzed in triplicate (more depending on time). Standard curve should cover potential range of analyte concentration, as an example if the expected concnetration is 50 ppm, a calibration curve should include many points (5-100 ppm) and be linear in that region. Additionally standard addition of a selected (potentially a not present pesticide which is spiked at a certain level) could be used in this case.
Mass Spectra for Atrazine (ESI Positive Mode):
Source is (4) Schreiber, A. "Application of spectral libraries for high-performance liquid chromatography-atmospheric pressure ionisation mass spectrometry to the analysis of pesticide and explosive residues in environmental samples." Journal of chromatography 869.1-2 (2000):411.
Atrazine Spectra: For Blog 7:
Davies J, Barquet A, Vaclavek C, et al. Human Pesticide Poisonings by a Fat-Soluble Organophosphate Insecticide. Archives of Environmental Health. December 1975;30(12):608.
Driss, M R. "Determination of carbaryl and some organophosphorus pesticides in drinking water using on-line liquid chromatographic pre-concentration techniques." Journal of chromatography 639.2 (1993):352-358.
Farran, A. "Identification of organophosphorus insecticides and their hydrolysis products by liquid chromatography in combination with UV and thermospray-mass spectrometric detection." Journal of chromatography 455(1988):163.
Feigenbrugel, V. "Near-UV molar absorptivities of acetone, alachlor, metolachlor, diazinon and dichlorvos in aqueous solution." Journal of photochemistry and photobiology. A, Chemistry 174.1 (2005):76
Sultatos, L G. "Determination of organophosphorus insecticides, their oxygen analogs and metabolites by high pressure liquid chromatography." Chromatographia 15.10 (1982):669.
Titanium Dioxide is a natural chemical that is used extensively in agriculture, cosmetic, food and coloring industry. Titanium dioxide, when used in colored industry, is an inorganic white pigment that is largely consumed in the coloring industry to enhance the opactiy, the whiteness and to achieve a desirable visual impact.(2)
The special chemical and physical features of Titanium dioxide as an inorganic white pigment are incorporated with other ingredients such as additives, colored pigments and resins in colored masterbatch production (masterbatch is a high concentrated pigment carrier for food & beverage packaging, cosmetic packaging, computer hardware production, etc) production. (1)
My interest is to recognize the nature of titanium dioxide in causing the coloration on color pigmented carrier (masterbatch) for plastic to be non-reproducible for one production to the next. When this happened, the quality control lab has to reformulate a more stable formula and remixing product has to be done.Reformulation is ideally to be avoided because it increases the capital cost of production for each batch and it influences customers' satisfaction on products made by the company. Through analytically studying the effect of titanium Dioxide in masterbatch, a method of study or a new technique could be devised and implemented to improve the production process of both white and colored masterbatches.(3)
My hypothesis is that titanium dioxide being larger in particle in comparison to other components in masterbatch formulation has lead to non-homogeneity of mixing and to cause a hindrace of pigment dyability in colored masterbatch production during coloration and pigmentation.
The analyte that I will focus on is Titanium Dioxide and it could be found in the mixture components of polymer resin, additives (antioxidants, Silicon oxide) and other inorganic pigments.
UV-Vis absorption spectrometry
The range of wavelength of titanium dioxide can be related closely to the preparation method of titanium oxide itself. For titanium dioxide with a commercial name Degussa P25 titanium dioxide (consists of 80% anatase and 20% rutile) that have been chemically treated with polymer compositions, it is found that the wavelengths of absorption for my analytes ranges from 400 to 600 nm. It is important to consider that this absorption spectra may be differed if some methods are not implemented when measurements are made such as the analyte has to subjected to low-temperature heat treatment above 350 K and making BaSO4 as a reference standard to the spectometer. (4)
Unfortunately, I could not find an optical density of my analyte within the wavelength range that I found from 400 to 600 nm. However, I found in source (5) that at wavelength 310 nm, titanium dioxide has an optical density of 0.8785. This data was found from a research paper that focused its interest of particle size measurement of titanium dioxide in safety of efficacy of nanotechnology.
In doing a research about UV-Vis absorption spectroscopy, I learnt that it will be a brilliant idea to narrow down my analytical problem to a particular method. So while finding more resources and getting more information from the class, I will attempt to assume that my analyte is prepared similarly with source (4).
Similiar Analytical Problem(s)
Exposure to Zinc Oxide and Titanium Dioxide Nanoparticles in Sunscreen by Heidi Nelson Heidi talks aboout the commercial uses of nanoparticles in sunscreen and its impact on human health and the environment. Her central hypothesis is to determine whether or not nanoparticles could be detected in blood or only present at the top layer of the skin after sunscreen's application on human's skin. The analytes for her analytical problem will be both zinc oxide and titanium dioxide nanoparticles and the matrix will be human skin and body. Other than the fact that we both focus on similiar analyte, I think my analytical problem mainly focus on particle size of the analyte and the optical properties that it has such as scattering of light, dispersion, etc.
For both our analytical problems, the optical properties of nanoparticles relate closely with a particle size and distribution, it is important to separate these nanoparticles by size and then measure the concentration according to the signal response making use of calibration curves. With these measurements, multiple sampling will help me to calculate and analyze the particle size distribution and how the content of TiO2 as our analytes. For my anaytical problem, I could analyze the deviation of other pigments and additives to mix homogenously and reproduce similar masterbatch production with both standard or previous masterbatch production.
In comparing the differences of studies between my analytical problem and Heidi's, it is important to recognize the matrix which in Heidi's case will be the human skin and the blood where in my case will be polymer resin or other pigments. With this being said, I think Heidi has to do separation before collecting the UV-vis spectra because she is dealing with analyte in more delicate yet complex matrix system. As for me, I will separate my analyte using a normal chromatography method to separate the nanoparticles and get a number to find the nanoparticle concentration later by using UV-vis.
Ahmed, S. I., Shamey, R., Christie, R. M. and Mather, R. R. (2006), Comparison of the performance of selected powder and masterbatch pigments on mechanical properties of mass coloured polypropylene filaments. Coloration Technology, 122: 282-288. doi: 10.1111/j.1478-4408.2006.00042.x (1)
Fisher, J. and Egerton, T. A. 2001. Titanium Compounds, Inorganic. Kirk-Othmer Encyclopedia of Chemical Technology.(2)
Russell, S. (2005) Color Compounding, in Coloring of Plastics: Fundamentals (ed R. A. Charvat), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/0471721581.ch18(3)
Vyacheslav, N. and Serpone, N. (2006) Visible Light Absorption by Various Titanium Dioxide Specimens, American Chemical Society. Russia. doi:25203 (4)
Delrieu, P. Particle Size Measurement of Attenuation Grade Titanium Dioxide in Diespersion and Sunscreen Lotion, Kobo products(5)
Blog 6- Chemical Structure and Standards
2. The chemical structure of my analyte, Titanium Dioxide (rutile form) is:
(accessed on October 24, 2011)
3. Information about my standards:
Company name: DuPont
Catalogue number: DuPont R-104 titanium dioxide
Quantity: 25 kg (packaged in polyethylene bag)
Price: Not available online (Need to contact local agent)
(accessed on October 24, 2011)
Blog 7- Atomic and Mass Spectrometries
The analyte that I will be looking for spectrometries will be Titanium dioxide. I think atomic spectrometries can be used to quantify the analyte of my analytical problem, however considering the preparation of analysis and a method to convert solid sample into solution suitable for analysis could be very time-consumptive and it also limits to eliminate the particle size effect application of titanium dioxide. Based on one study I found, ICP-OES/MS can be employed using slurry nebulization and electrothermal vaporization to deal with solid sample, therefore this will be desirable for my analytical problem in excluding out all the impurities before quantifying the concentration of titanium dioxide.
JOURNAL OF MASS SPECTROMETRY
J. Mass Spectrom. 2006; 41: 1378-1385
Published online 29 September 2006 in Wiley InterScience
(www.interscience.wiley.com) DOI: 10.1002/jms.1111
Blog 11. Capillary Electrophoresis Techniques
1. Capillary Zone electrophoresis is only good to separate ionic species based on their charge, where MEKC (Micellar Electrokinetic Chromatography) is mostly used to separate DNA and proteins (or biomolecular compounds). Capillary Isoelectric Focusing Electrophoresis) is done based on the isoelectric measure or pH of the analyte. Due to this reasoning, the best separation technique of CE would be CGE (Capillary Gel Electrophoresis).
2. The type of capillary electrophoresis that is most suitable to separate my analyte from other matrix components in my sample is Capillary Gel Electrophoresis (CGE). This is because all other CE techniques separates the components based on charge of the analyte. On the other hand, CGE allows separation to occur based on particle sizes and multiple particle shapes and since my hypothesis require me to test on parameters like particle distribution and particle size, CGE will be a good technique in analyzing my analyte in matrix. It also allows me to do multiple runs in parallel on the same gel with optimized conditions.
3. Suitable conditions of using CGE as a technique:
Buffer composition:0.5x TBE (Tris-borate EDTA buffer)
Electric field used:150 V
Capillary type: Coating of 100% SH-PEG-COOH
4. I would use a Transmission Electron Microscopy for my detector. It is because electrophoretic mobilities can be quantitatively measure based on the gel mobilities of polymer coated nanoparticles and an image of the interacted electrons transmitted could be obtained to detect this phenomenon.
Separation of Nanoparticles by Gel Electrophoresis According to Size and Shape
Matthias Hanauer, Sebastien Pierrat, Inga Zins, Alexander Lotz, and Carsten Sönnichsen*
Institute for Physical Chemistry, University of Mainz, Jakob-Welder-Weg 11, 55128 Mainz, Germany
Posting due by 9:04 AM on Sep 21, 2011.
The dowloadable pdf provides:
This blog also has examples of posters presented in the past. See entries under the "Posters" category.