Citation:

FRICKE, M., M. ZELLER, S. CONKLIN, P. A. CREED, C. A. SCHWEGEL, M. WITKOWSKI, AND JOHN T. CREED. DIMETHYLITHIOARSINIC ANHYDRIDE: A STANDARD FOR ARSENIC SPECIATION. Presented at Pittsburg Conference, Orlando, FL, March 12 - 16, 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:

Recently, sulfar analogs of well know arsenicals have been identfied in biolgical, dietary and environmental matrices. These discoveries have generated a need for stable species-specific standards. This presentation will forcus on the isolation and characterization of a standard for dimethylthioarsinic acid. Dimethylthioarsinic acid (DMTA) is a naturally occurring arsenical that has recently been identified as a potential arsenic arcinogen. To date, determination of this species has been by chromatographic retention time to match to analytical standards generated in vitro by the reaction of dimethylarsinic acid (DMA) with hydrogen sulfide (H₂S). The reaction generates multiple arsenic-containing products which has hampered the isolation of the initially formed species, DMTA. This was overcome by chromatographic monitoring of the formation of the products from DMA + H₂S. The reaction was iteratively advanced until 90% of the DMA starting material was converted to DMTA. No other products were observed at this point in the reaction progress. Isolation of DMTA was by organic techniques and facialitated by the solubility of the product in nonpolar media as compared to the starting material. Single crystal diffraction demonstrated that DMTA as a solid had been isolated as the oxygen-bridged dimethylthioarsinic anhydride. The anhydride form of DMTA was determined as a suitable standard because of the ease of isolation, the long term stability of the crystalline standard, and the rapid conversion of the anhydride to the acid upon dissolution in water.

Record Details: