Determination of trace impurities in high-purity niobium by inductively coupled plasma atomic emission spectrometry after anion-exchange separation

Abstract

Inductively coupled plasma atomic emission spectrometry (ICP-AES) in combination with anion exchange with hydrochloric and hydrofluoric acid media was applied to the determination of trace-metal impurities in high-purity niobium samples. The column operating conditions of the anion-exchange method were selected on the basis of the mass distribution coefficients of the analytes. Molybdenum, tungsten and titanium having similar chemical properties to niobium were eluted simultaneously with magnesium, manganese and chromium. Iron and tantalum were eluted after niobium had been removed. These trace impurities were determined by ICP-AES using analysis lines that were free from spectral interference from the small amount of niobium which was present in the effluents. The results obtained for high-purity niobium oxide and niobium metal samples using ICP-AES combined with an anion-exchange method, agreed well with those obtained by electrothermal atomic absorption spectrometry without the separation of niobium and ICP-AES combined with a solvent extraction method.