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Nate Vetter - Analytical Problem - Nanoparticles Accumulate in the Food Chain

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

View image

Standards:

Company: Nanocs7
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


References:

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

Comments

Blog 13 - As describes the potential cannot be used for simultaneous quantification and identification. References? -0.5 pt.

Using a Electrolytic cell one half comprised of a copper electrode, copper sulfate solution and the other of my sample analyte solution separated by a salt bridge to a solution of silver ions you can measure the potential between the two half cells. This potential will tell you both that there is analyte present in the sample solution and how much analyte based on the potential measured.

Je vous apprécie pour votre grande surprise réfléchie d'avoir écrit ce court article. Le message semble etre transmises a moi en particulier. Notre fils avait aussi beaucoup a apprendre de lui - meme s'il a été celui qui a découvert votre site en premier. Chacun d'entre nous ne peut imaginer un cadeau plus fantastique que d'un don pour vous encourager a faire plus.

Blog 9. What is the analyze size range for the column that you choose? (-0.1 pt).
Blog 10. Good answer.
Blog 11? (-1 pt).

Problems using similar techniques
One of the preferred analytical techniques for my analytical problem is ICP-MS. This technique can detect small amounts of analyte within complex matrices. ICP-MS also has the smallest work up to prepare my samples for use in the instrument allowing for more time spent on analyzing the data rather than running the instrument.

Similar techniques that are using ICP-MS
Revy Saerang - Titanium Dioxide in Masterbatch
Joe Zibley - I-131 in Japanese Milk Supply
Heidi Nelson - Exposure to Zinc Oxide and Titanium Dioxide Nanoparticles in Sunscreen

Chromatographic technique

Among the types of chromatographys discussed in class ion exchange or size-exclusion chromatography most likely could assist in separation of silver nanoparticles from my matrix. But for my analytical problem I will use size exclusion chromatography due to its cutting edge approach. Normally nanoparticles are lost in the column due to irreversible adsorption to the column but using surfactants can remove that problem.

Instrument: HP 1050 chromatograph with a HP-1100 DAD detection system and a HP Chemstation datastation (Hewlett-Packard, Palo Alto, CA). This detection system enables a simultaneous measurement of absorption from 190 to 950 nm (UV−vis−NIR).
Sample injections: 10-μL
Column: Nucleogel GFC 1000-8 column (Macherey-Nagel, Düren, Germany) of 300 × 7.7 mm, 100-nm pore size and 8-μm particle size, with a precolumn filter (0.45 μm, Rheodyne, Cotati, CA)
Flow rate: typical flow rate of 1.0 mL/min, but can vary
Mobile phase: Sodium dodecyl sulfate (SDS, purity >95%),Polyoxyethylene (23) dodecanol (Brij-35) and H2O

Wei, G. T.; Liu, F.K.; Wang C. Shape Separation of Nanometer Gold Particles by
Size-Exclusion Chromatography. Anal. Chem. 1999, 71, 2085-2091

Good answers

Sample Preparation Procedure
Prep for ICP-MS
1. Digestion/microcentrifuge - Using microliters of hydrochloric acid and hydrogen peroxide, digest the tissues of both the worms or food source. Centrifuge the sample to extract the silver from the matix. Bring to 3 ml volume for ICP-MS analysis.

Prep for other analysis (UV-Vis, IR, etc.)
1. Digestion/microcentrifuge - separate the samples from the matrix using the same process above.
2. Filter – Filter the silver nanoparticles – pores on filter should remove debris in sample but not impede nanoparticles.
3. Size exclusion chromatography (SEC) – Knowing how small the nanoparticles are, SEC will allow for purification of the nanoparticles as they will elute out last. Discovering the solvent to run this with would be done using standards before trying the sample to determine approximate elution times, solvents, and flow rates.
4. Dry/Store – Rotovap to remove solvents and store till needed

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

Wei, G. T.; Liu, F.K.; Wang C. Shape Separation of Nanometer Gold Particles by
Size-Exclusion Chromatography. Anal. Chem. 1999, 71, 2085-2091

Blog 6. Good answers.
Blog 7. Example of mass spectrum? (-0.1 pt)

Atomic and mass spectrometries

Detecting Silver Nanoparticles: Ag

Analyze at 328.1 nm for AAS (Atomic Absorption Spectrometry)

Reason: Due to the exact purpose of the instrument being to detect small atoms, AAS is perfect for detecting even small amounts of silver nanoparticles.

Mass Spectrometry:

Ag+ : atomic weight about 108

Method: ICP-MS due to analyzing soil/solids for trace amounts of silver nanoparticles.

Analytical Methods. Determining Silver in Biological Materials. http://www.atsdr.cdc.gov/toxprofiles/tp146-c6.pdf (accessed Oct 28, 2011)

BLOG 4. What about studies used to test the second part of the hypothesis? "In turn animals and insects alike, can uptake these nanoparticles and the nanoparticles can translate up the food chain as predators eat the prey."? (-0.5 pt).

BLOG 5. OK

Fluorescence Techniques:
Silver nanoparticles do not fluoresce but can be characterized by infrared spectroscopy. Ag0 has a broad fingerprint region and a clearly defined peak at a frequency of ~2480 cm-1. IR can be useful in determining the presence but not necessarily concentration of silver nanoparticles. Using a control, analysis of samples from worms with and without nanoparticles will result in two IR spectra that can be compared to determine the presence of the nanoparticles. Due to the lack of information obtained from IR, I would not recommend this technique as the primary method of determining the concentration of silver nanoparticles. The nanoparticles only create small changes in the IR spectra and do not provide the necessary information to calculate amounts or even size of the nanoparticles. Even worse, unless the sample is fully removed from the matrix and separated, other molecules could cover up (also have a vibration at a frequency of 2480 cm-1) the small concentrations of silver nanoparticles present. I believe that UV-VIS still will play a larger role than IR in my analytical problem.

Sreeram, K. J.; Nidhin, M.; Nair, B. U. Microwave Assisted Template Synthesis of Silver Nanoparticles. Bull.Matter.Sci. 2008, 31 (7), 937-942.

Zhang, L.; Yu, J. C.; Yip, H. Y.; Li, Q.; Kwong, K. W.; Xu, A.; Wong, P. K.; Ambient Light Reduction Strategy to Synthesize Silver Nanoparticles and Silver-Coated TiO2 with Enhanced Photocatalytic and Bactericidal Activities. Langmuir. 2003, 19, 10372-10380.

Hypothesis: 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.

Studies: (A) Identify Waste streams with nanoparticles present. Determine greatest area of concentration of silver nanoparticles. (B) Measure concentration of silver nanoparticles in soils near waste streams of interest. (C) Based on concentrations of silver nanoparticles found in soils, construct a study similar in the lab using concentrations below, at, and above to determine the effect on accumulation in worms or other insects.

Alternative Study: (D) If soils are not found to contain high enough concentrations of silver nanoparticles, then testing the waste water would be the next Course of action. (E) Testing retention of Silver nanoparticles in soil from waste water would need to be performed.

Rough estimates on concentrations needed for studies:

Soil samples: 40-90 mg Ag per Kg Soil

Waste Water samples: 100 mg Ag per L waste water

Topic has been adjusted to fit new criteria. New topic consists of silver nanoparticles (I know huge change :P ) and their transfer up the food chain. This has a more realistic analyte still being used as an antimicrobial in household products.

Heidi Nelson - Exposure to Zinc Oxide and Titanium Dioxide Nanoparticles in Sunscreen

This analytical problem is similar to mine because it also involves nanoparticles and exploring the consequences of nanotechnology for living organisms. Similar techniques would likely be used in both cases to detect and characterize nanoparticles in biological matrices. Both of these analytical problems have implications related to the safety of nanotechnology in commercial products.

Posting is good. There is no need to describe potential techniques yet. Why are you focusing on gold? Are they a prevalent type of particle in the waste? This type of analyte will need to be revisited (-0.1 pt)