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

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 Nb 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 Ti having similar chemical properties to Nb were eluted simultaneously with magnesium, Mn and Cr. Iron and Ta were eluted after Nb 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 Nb which was present in the effluents. The results obtained for high-purity niobium oxide and Nb 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 Nb and ICP-AES combined with a solvent extraction method. 23 ref.--AA