Determination of trace amounts of thallium in commercial radioactive 204Tl samples by the Redox sub-superequivalence method of isotope dilution analysis

Trace amounts of thallium in a commercial radioactive 204Tl sample were determined using the sub-superequivalence method of isotope dilution analysis (SSE-IDA) and sub-stoicheiometric isotope dilution analysis (Subst-IDA), and the results obtained were compared. Before the determination, various conditions for oxidation and extraction were examined. An HCl-HClO4 mixture was the best solvent for oxidation by KBrO3 and 20% tributyl phosphate in benzene was suitable for the separation of Tl111. Under conditions where ordinary Subst-IDA gives large errors, accurate determinations with errors of a few per cent were possible with SSE-IDA. The volume of the reaction solution was minimised in order to reduce the radioactive waste problem. (author)