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Analysis of Arsenicals and Their Sulfur Analogs in Biological Samples Using HPLC with Collision Cell ICP-MS and ESI-MS/MS
Citation:
GALLAWA, C., K. KUBACHKA, P. A. CREED, JOHN T. CREED, M. J. KOHAN, K. HERBIN-DAVIS, AND D. J. THOMAS. Analysis of Arsenicals and Their Sulfur Analogs in Biological Samples Using HPLC with Collision Cell ICP-MS and ESI-MS/MS. Presented at 35th FACSS, Reno, NV, September 28 - October 02, 2008.
Impact/Purpose:
Develop analytical approaches to quantify reactive intermediates within the metabolic pathway that biotransforms inorganic arsenic to DMA(V). The ability to quantify these species will enhance the mode of action (within NHEERL) and the bioavailability / bioaccessibility research (within NERL).
Description:
Recent arsenic speciation studies have indicated that the sulfur analogs of the more common arsenic oxides are present in environmental and biological systems. This discovery was previously impeded due to the strong affinity of these arsenic-sulfides for the stationary phases typically used in arsenic oxide based speciation studies. The presence of thiolated arsenicals adds to the chromatographic resolution requirements essential for elemental-based detection (ICP-MS), mainly because misidentifications of an unknown can be made when relying solely on retention time matching when using element specific detection systems. The need for complementary molecular based information using techniques, like LC-ESI-MS/MS, have proven beneficial for assigning molecular structures to unknown arsenicals within complex matrices. The need is also especially important in indentifying the thiolated arsenicals, because primary standards of the neat materials are not commercially available. The detection of thiolated arsenicals as urinary metabolites in both animals and humans has raised questions regarding how and when these species are produced within the metabolic pathway of arsenic. The authors have previously indicated that the microflora in the cecum of a mouse are able to biotransform an arsenosugar oxide (a tri-alkyl substituted arsenic oxide) to its corresponding sulfide [1]. This biotransformation raises questions regarding the conversion of structurally similar arsenic oxides, such as dimethylarsinic acid (DMA, di-alkyl substituted arsenic oxide). This presentation will summarize the analytical data from both LC-ICP-MS and LC-ESI-MS/MS that confirms the production of dimethylthioarsinic acid (DMTA) in the cecum of a mouse. The presentation will also report on the use of an isotopically enriched sulfur label to distinguish between proposed metabolic pathways. Finally, some preliminary research on the conversion of inorganic arsenic to its sulfur analogs will be presented.