EXTRACTIVE SEPARATION AND DETERMINATION OF THALLIUM AND INDIUM BY LIQUID SCINTILLATION-COUNTING

A simple and rapid method is proposed for the extractive separation of trace amounts of thallium and indium by extraction with trioctylamine from chloride and iodide medium at different concentrations of H2SO4. The beta-activities of Tl-204 and In-114 were measured by liquid scintillation counting. The extracted thallium was stripped with 0.2 mol l(-1) Na2SO3 and determined by substoichiometric isotope dilution analysis using Victoria Blue B as the reagent from 0.5 mol l(-1) HCl. The method was found to be useful for determination of thallium in rock samples, cadmium oxide, city waste incineration ash, sewage sludge and high-purity indium metal. In-III was extracted from iodide medium and stripped with 0.2 mol l(-1) ammonium acetate. The stripped indium was determined using a substoichiometric amount of Aliquat-336 as the reagent from 0.7 mol l(-1) KBr and 4.0 mol l(-1) H2SO4. The method was applied to determine indium in rock samples, cadmium oxide, zinc ore, silicon wafer, zinc metal and stream sediments. The co-extracted ions were removed by the use of appropriate masking agents.