SUBSTOICHIOMETRIC ISOTOPE-DILUTION ANALYSIS OF ARSENIC IN BIOLOGICAL AND ENVIRONMENTAL STANDARD REFERENCE MATERIALS BY SOLVENT-EXTRACTION USING TOLUENE-3,4-DITHIOL IN BENZENE

A radiochemical solvent extraction procedure has been developed for ti le determination of As(III) using As-76 tracer. It is based on the com plexation of As(III) with toluene-3,4-dithiol (TDT) at pH 2 and subseq uent extraction in benzene. The effect of various parameters such as p H, lime of equilibration, nature of solvent, quantitative character an d interferences have been studied. The method has been further develop ed into substoichiometric isotope dilution analysis for the determinat ion of As at < 1 mu g level and employed for the analysis of several e nvironmental and biological standard Reference Materials from NIST (US A), IAEA (Vienna) and NIES (Japan).