Determination of small amounts of molybdenum in niobium and tantalum by atomic-absorption spectroscopy in a nitrous oxide-acetylene flame

Abstract

Between 0·006 and 0·06 per cent. of molybdenum can be determined in niobium or tantalum by extracting molybdenum(VI) 8-hydroxyquinolinate from a medium containing fluoride and EDTA as masking agents into butanol at pH 4·5, and atomic-absorption spectroscopy of the extract in a nitrous oxide-acetylene flame at 3132 Å without recourse to scale expansion. The most suitable conditions for the determination have been established, and a study of the effect of other cations and anions is presented. Vanadium(V) and chromium(VI) interfere when present in 100-fold excesses, but their interference can be eliminated by the addition of potassium sulphite to the solution before extraction.