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EPA STUDIES OF ARSENIC SPECIATION IN SEAFOOD MATRICES WITH AN EMPHASIS ON EXTRACTABILITY AND ARSENOSUGAR INTEGRITY
Citation:
Creed, J T., P A. Gallagher, C A. Schwegel, A Parks, AND B. M. Gamble. EPA STUDIES OF ARSENIC SPECIATION IN SEAFOOD MATRICES WITH AN EMPHASIS ON EXTRACTABILITY AND ARSENOSUGAR INTEGRITY. Presented at 2002 Pittsburgh Conference, New Orleans, LA, March 17-22, 2002.
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 anthropogenic and geological occurrence of arsenic (As) results in human exposure to a potentially carcinogenic element. The two predominant pathways to As exposure are drinking water (DW) and dietary ingestion (DI). DW exposures are almost exclusively toxic inorganic As. This toxicity has led to the reformulation of the MCL for As and increased the number of DW sources which requires some type of treatment. The effectiveness of this treatment can be influenced by the oxidation state of the inorganic As present in the water. Therefore, deciding which treatment to use often requires the inorganic As be speciated (separated) into As(III) and As(V). The preservation of this natural distribution during shipment can be problematic, especially in iron rich waters. The first part of this presentation will describe a systematic evaluation of factors which can influence the preservation of As. An emphasis will be put on the use of the EDTA in combination with acetic acid to stall or inhibit the iron precipitation reactions which produce "FeOAs"solids. Five DWs will be evaluated and the stability of their native As distribution in time will be discussed. The second major source of As exposure is DI, with seafood representing over 50% of the total dietary exposure. From a total metal perspective, dietary As exposures can easily exceed those from DW, especially in populations with high seafood consumption rates. Unlike DW, dietary As is a mixture of toxic and non-toxic arsenicals [e.g., AsB, arsenosugars, etc.]. For this reason, to assess toxicity from dietary exposures, it is necessary to speciate the As. The extraction of arsenicals from solid seafood matrices gives rise to concerns regarding the species specific stability and the need to minimize spcies specific extraction bias. However, there is uncertainty as to whether or not the native arsenical distribution in the matrix reflects what elutes from the chromatographic column, Aggressive extraction condidtions can lead to a more quantitative removal but may produce arsenosugar degradation products. This presentation will provide some preliminary data indicating that some arsenosugars tend to bind to secondary substrates making them difficult to chromatograph by conventional anion IC. Most of the results will be collected using IC-ICP-MS, and IC-ESI-MS/MS will be used in an attempt to provide structural informatoin on degradation products.