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DETECTION AND QUANTIFICATION OF THIO-ARSENOSUGAR IN MARINE MOLLUSKS BY IC-ICP-MS WITH AN EMPHASIS ON THE INTERACTION OF ARSENOSUGARS WITH SULFIDE AS A FUNCTION OF PH
Citation:
CONKLIN, S., P. A. CREED, AND JOHN T. CREED. DETECTION AND QUANTIFICATION OF THIO-ARSENOSUGAR IN MARINE MOLLUSKS BY IC-ICP-MS WITH AN EMPHASIS ON THE INTERACTION OF ARSENOSUGARS WITH SULFIDE AS A FUNCTION OF PH. JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY. Royal Society of Chemistry, Cambridge, Uk, 21(9):869-875, (2006).
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 sulfar analog of As(328)(2,3-dihydroxypropyl-5-deoxy-5-dimethylarsinoyl-ß-D-riboside), abbreviated (As(328-S), was detected and quantified in five species of marine shellfish using IC-ICP-MS with structural verification via IC-ESI-MS/MS. The CAD spectra produced from the parent ion m/z 345 in the extract contained two major daughter ions, m/z 253 and 235, closely matching the CAD spectrum of synthetic As(328-S). The ability of the oxide and sulfide forms of the arsenosugar to interconvert led to a series of fundamental studies in ideal solutions containing both the arsenosugar and sulfide. The conversion of As(328) to As(328-S) was found to be pH sensitive, and promoted in the pH range where HS- is converted to H2 (pK1 = 7). The conversion was observed in both shellfish extracts and ideal solutions with comparable sulfide and arsenosugar concentrations. The conversion was further studied over a range of sulfur/arsenic molar ratios. At a 15-fold molar excess of sulfide at pH 4.8, the lowest pH experienced by an extract, > 90% conversion to the sulfide was observed. In the context of shellfish, a molar ratio greater than 200:1 sulfide to arsenic was detected in all five extracts. These trends should prove useful in improving confidence in thio-arsenosugar speciation, and predicting the extent of conversion under a given set of conditions.