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ARSENIC SPECIATION IN CARROT EXTRACTS WITH AN EMPHASIS ON THE DETECTION OF MMA(III) AND MMTA
Citation:
YATHAVAKILIA, S. K., M. FRICKE, P. A. CREED, C. A. SCHWEGEL, AND JOHN T. CREED. ARSENIC SPECIATION IN CARROT EXTRACTS WITH AN EMPHASIS ON THE DETECTION OF MMA(III) AND MMTA. Presented at 2006 Winter Conference on Plasma Spectrochemistry, Tucson, AZ, January 08 - 14, 2006.
Impact/Purpose:
To develop an arsenic speciation protocol for the analysis of dietary components and composite diets in order to provide a more accurate assessment of human exposure to arsenicals.
Description:
The two predominant routes of arsenic exposure are dietary ingestion and drinking water consumption. Dietary arsenic, unlike drinking water arsenic, contains a variety of arsenicals with dramatically different toxicities. The list of arsenicals detected in dietary samples continues to grow with recent emphasis on sulfur-containing analogs of arsenic oxides and the ability to differentiate between the oxidation states of methylated arsenicals. This can be partially explained by the mechanistic research, which has begun to indicate that sulfur analogs of dimethylarsinate {DMA} [1], as well as the species methylarsonite {MMA(III)} and dimethylarsinite {DMA(III)} [2], profoundly influence the observed toxicity. The scientific consensus that inorganic arsenic is detoxified via methylation is being questioned, as MMA(III) and DMA(III) may be activated intermediates that could be associated with the carcinogenicity of As during the methylation pathway in vivo [2]. Because of these recent findings, researchers have attempted to use analytical procedures to preserve the native oxidation state in both biological and dietary matrices.
In previous studies, some varieties of carrots were found to contain monomethylarsonate {MMA(V)} and a species that was tentatively identified as MMA(III), in addition to inorganic arsenic [3]. This presentation will provide arsenic speciation data in carrots using a mass balance approach. The emphasis of the presentation will be on the chromatographic data, which indicates that both MMA(III) and monomethylthioarsenic acid {MMTA} are present in low levels in some carrot extracts. Data for carrot extracts fortified with MMA(III) will be presented demonstrating co-elution via IC-ICP-MS. Co-elution on a secondary chromatographic column using IC-ICP-MS will be presented to further substantiate the presence of MMA(III) in the carrot extract. Similar data will be presented for the occurrence of MMTA in carrot extracts. To date, molecular confirmation via IC-ESI-MS/MS has been unsuccessful due to the low concentrations of MMA(III) and MMTA in carrots.
[1] K. Kuroda, G. Endo, et al., Toxicology and Applied Pharmacology, 2004, 198, 345.
[2] T.G. Rossman, A.N. Uddin, F.J. Burns, Toxicology and Applied Pharmacology, 2004, 198, 394.
[3] N.P. Vela, D.T. Heitkemper and K.R. Stewart, Analyst, 2001, 126, 1011.