CHARACTERIZATION OF ORGANIC ARSENIC COMPOUNDS IN BIVALVES

Water-soluble arsenic compounds were extracted with methanol/water (1:1, v/v) from various species of bivalves and also from certified reference materials (NIES No. 6, mussel tissue, and NBS 1566, oyster tissue). The extracts were analyzed with a high-performance liquid chromatograph combined with an inductively coupled argon plasma mass spectrometer serving as an arsenic-specific detector. A certified reference material (NIES No. 6) was used to check the reproducibility of the analysis. The relative standard deviations (RSDs) of the peak area of major arsenic compounds among repeated measurements (n = 6) on the same extract were less than 3.3%, indicating good reproducibility of the technique. The RSDS Of some peaks among measurements of independent extracts, on the other hand, were more than 10%. possibly reflecting the heterogeneity of the sample in terms of the chemical species under the present experimental conditions. In many of the samples analyzed in the present study, two arsenic-containing ribofuranosides were detected in addition to arsenobetaine. A compound bearing a glycerophosphoryl glycerol moiety was dominant in such cases. Interestingly, a bivalve living in an estuary (Corbicula japonica) did not contain a detectable amount of arsenobetaine though it had arsenic-containing ribofuranosides. The distribution of arsenic species in the various parts of a clam (Meretrix lusoria) and a mussel (Mytilus coruscum) was also analyzed.