ICP-MS for the Determination of Heavy Metals in Dietary Supplements, Part 3

See Introduction here.

See Results here.

See Instrumentation here.

Future of the field
An important area of future research in this field is the optimization of the method for speciation analysis. For certain metals such as mercury, arsenic, or chromium, the form of the element is an important factor in its toxicity. Some elements like selenium can be toxic in certain configurations yet is necessary for a variety of biological processes. By combining ICP-MS with various chromatographic separation techniques, such as HPLC, these various species can be differentiated. However, there are certain drawbacks that must be overcome for more widespread use of this technique. First of all, speciation can be limited by chromatographic retention times, and there may be metal contamination due to the chromatography system. Another problem is that the mobile phase of the separation can greatly influence the stability and ionization power of the plasma. To improve this, much research is being put into nano-scale chromatographic couplings.

Selenium Compounds, MiPe. Wikipedia

As a next step in the advancement of this technology, I would propose an experiment which uses lCP-MS to detect metal-based pesticides in dietary supplements. Inorganic pesticides can contain copper, lead or arsenic, while organometallic pesticides often use methyl-mercury. Pesticides are often detected using HPLC, but it should be possible to differentiate metals from pesticides versus those from other sources by ICP-MS alone. To achieve this, careful optimization will be necessary, and controls would have to be made containing pesticide spiked samples as well as samples spiked with the metals alone. The metals configurations in the pesticide along with the other unique interfering species should create subtle differences in the way the pesticide-Iaced sample molecules interact with the inert gas in the instrument, creating detectable differences. Reaction cell mode would have to be used, and the proper reactive gas would have to be identified based on the organic components of the pesticides.

References

1. Avula, Wang, Duzgoren-Aydin, Khan. Inorganic elemental compositions of commercial multivitamin/mineral dietary supplements: Application of collision/reaction cell inductively coupled-mass spectroscopy Food Chemistry Volume 127, Issue 1, 1 July 2011, Pages 54-62

2. Ducos, Hamester,and Godula. ICP-MS for Detecting Heavy Metals in Foodstuffs, Food Quality magazine. February/March 2010 http://www.foodquaIity.com/details/article/809781/ICPMS_for_Detecting__Heavy_Metals_in_Foodstuffs_.htm|?tzcheck=1

3. Moret, Prevarin, Tubaro. Levels of creatine, organic contaminants and heavy metals in creatine dietary supplements. Food Chemistry Volume 126, Issue 3, 1 June 2011, Pages 1232-1238

4. http://www.chem.agilent.com/Library/applications/5989-7959EN.pdf

5. http://www.perkinelmer.com/CMSResources/lmages/441303453pp_determinationofmetaIsindietarysupplements.pdf