ONLINE ION-EXCHANGE SEPARATION AND DETERMINATION OF NIOBIUM, TANTALUM, TUNGSTEN, ZIRCONIUM AND HAFNIUM IN HIGH-PURITY IRON BY FLOW-INJECTION INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

A study was made to investigate the feasibility of using an anion-exchange resin for on-line separation of trace amounts of niobium, tantalum, tungsten, zirconium and hafnium from iron matrix samples. The incorporation of a micro-column packed with Dowex 1X8-100 ion-exchange resin into a now injection system is presented. The detection was done with inductively coupled plasma mass spectrometry (ICP-MS). The sample treatment, optimization of analytical variables and measurable concentration levels are discussed. Recoveries from standard additions to a high-purity iron were for all the analytes close to 100%, with relative standard deviations ranging from 0.7 to 3.0%. The limits of quantification (10 s(n-1)) calculated from a 5% (m/v) iron sample solution were 8, 5, 14, 12 and 10 ng g(-1) for Nb, Ta, W, Zr and Hf, respectively. The accuracy of the proposed method was tested by determining these elements in Euronorm-CRM 098-1 reference material. Recoveries from 0.250 g test portions of the above reference material spiked with 2.5 and with 12.5 ng each of the five analytes are reported.