Purification of Hf in silicate materials using extraction chromatographic resin, and its application to precise determination of176Hf/177Hf by MC-ICP-MS with179Hf spike

Abstract

A two-stage column purification method for Hf from Zr and other elements in silicate samples using the extraction chromatographic resin, UTEVA has been developed. In the first column, using an anion-exchange resin, AG 1X8, Hf, Zr and Ti were collected. In the second, using UTEVA, and after eliminating F− by evaporation with HClO4 and re-dissolution with H2O2–HNO3, Hf was purified from Ti and Zr, based on characteristic of the UTEVA resin that Hf distribution coefficient (Kd) decreases from 770 to 40, while Kd of Zr decreases less from 890 to 200, in 9 and 6 mol l−1 HNO3, respectively. The recovery yield of Hf was ∼88% and total blank was ∼4 pg. A MC-ICP-MS Hf isotope ratio determination method was also developed, which uses 179Hf spike for simultaneous determination of the Hf concentration and 176Hf/177Hf ratio. Combining the chemistry and ICP-MS techniques, 176Hf/177Hf ratios in silicate reference materials were determined with and without the spike, which gave identical results, showing the applicability of this method.