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 the determination of As(III) using As-76 tracer. It is based on the complexation of As(III) with toluene-3,4-dithiol (TDT) at pH 2 and subsequent extraction in benzene. The effect of various parameters such as pH, lime of equilibration, nature of solvent, quantitative character and interferences have been studied. The method has been further developed into substoichiometric isotope dilution analysis for the determination of As at < 1 mu g level and employed for the analysis of several environmental and biological standard Reference Materials from NIST (USA), IAEA (Vienna) and NIES (Japan).