Accuracy in the Isotope Dilution Mass Spectrometry of Uranium in Rubidium Uranium Sulphate Rb2U(SO4)3

Abstract

Problems encountered in the determination of uranium in rubidium uranium sulphate (Rb₂U(SO₄)₃) employing isotope dilution thermal ionisation mass spectrometry (ID-TIMS) are discussed. The positive bias of 0.2 to 0.3% in the determination of uranium in Rb₂U(SO₄)₃ by ID-TIMS with respect to the stoichiometric composition has been resolved by modifying the chemical exchange procedures. The concentration of uranium in Rb₂U(SO₄)₃ could be determined with an accuracy better than 0.1% employing the HClO₄ treatment for proper isotopic exchange between the spike and sample isotopes.