Matt Marah - Analytical Problem: Cadmium Levels in Blood
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.