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INVESTIGATION OF ARSENOSUGAR-SUBSTRATE INTERACTIONS IN SEAFOOD EXTRACTED WITH TETRAMETHYLAMMONIUM HYDROXIDE
Citation:
Gamble, B. M., P A. Gallagher, J A. Shoemaker, A. Heck, D M. Freeman, C A. Schwegel, AND J T. Creed. INVESTIGATION OF ARSENOSUGAR-SUBSTRATE INTERACTIONS IN SEAFOOD EXTRACTED WITH TETRAMETHYLAMMONIUM HYDROXIDE. Presented at 2002 Winter Conference on Plasma Spectrochemistry, Scottsdale, AZ, January 6-12, 2002.
Impact/Purpose:
The goal is to develop an extraction protocol that mimics the human digestive tract and then to use it to assess the bioavailable fraction of arsenic from complex dietary mixtures such as a daily composite -- to move current methods toward a better human physiologically-based exposure estimate method which approximates the "true" bioavailability of arsenic within an environmental or dietary matrix.
Description:
The maximum contaminate level (MCL) for arsenic is currently being revised within the U.S. Safe Drinking Water Regulations. The proposed MCL is 10 ng/g. The formulation of this MCL is influenced by a wide variety of factors including risk assessments based on health data, best available treament technology, analytical monitoring capability and relative exposure source estimates. The relative exposure source estimate is formulated to assess the exposure from all possible routes. For arsenic, the two major exposure routes are dietary and drinking water ingestion. The uncertainty associated with dietary exposure source estimates is relatively high because species specific data on target foods is limited and poor extraction efficiencies in certain seafood samples makes species specific risk assessment difficult.
The uncertainty generated by poor extraction efficiencies can be minimized by using a more aggressive extraction solvent, such as tetramethylammonium hydroxide. When a more aggressive technique is employed, a larger percentage (90+%) of the available arsenic is liberated into solution from the solid seafood matrices. The resulting solution contains "substrates" which can bind native arsenosugars and result in a "substrate-arsenosugar" complex that is unchromatographable using anion exchange chromatography. Currently, the substrate is thought to be a protein or lipid with a molecular mass of less than 10 kDa. In addition, the resulting complex is acid-labile at pH 4. This poster will investigate the nature of the arsenosugar-substrate interaction and attempt to identify the substrate using size exclusion chromatography with ICP-MS and ESI-MS/MS detection. By better understanding the arsenosugar-substrate interaction, a more quantitative, species-specific arsenic risk assessment can be established for dietary exposure in seafood samples.