Extractive separation and determination of thallium and indium by liquid scintillation counting

Abstract

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 β-activities of ²⁰⁴Tl and ¹¹⁴In were measured by liquid scintillation counting. The extracted thallium was stripped with 0.2 mol l^–1 Na₂SO₃ and determined by sub-stoichiometric 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 sub-stoichiometric 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.