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 scin tillation counting. The extracted thallium was stripped with 0.2 mol l (-1) Na2SO3 and determined by substoichiometric isotope dilution analy sis using Victoria Blue B as the reagent from 0.5 mol l(-1) HCl. The m ethod was found to be useful for determination of thallium in rock sam ples, cadmium oxide, city waste incineration ash, sewage sludge and hi gh-purity indium metal. In-III was extracted from iodide medium and st ripped with 0.2 mol l(-1) ammonium acetate. The stripped indium was de termined using a substoichiometric amount of Aliquat-336 as the reagen t from 0.7 mol l(-1) KBr and 4.0 mol l(-1) H2SO4. The method was appli ed to determine indium in rock samples, cadmium oxide, zinc ore, silic on wafer, zinc metal and stream sediments. The co-extracted ions were removed by the use of appropriate masking agents.