A straightforward separation scheme for the concomitant isolation of Lu, Hf, Sm, and Nd prior to isotope ratio and isotope dilution measurements following sample decomposition by Lithium metaborate fusion or Hydrofluoric acid dissolution

Abstract

A robust method is described allowing the sequential separation of Hf and the lanthanides from matrix elements of silicate rocks or minerals. This is based on a single chromatographic column filled with the conventional cation-exchange DowexAG50W-X8 resin, and hydrochloric, nitric and sulfuric acids as eluting agents. Samples can be processed following the same column protocol, irrespective whether they were decomposed by high temperature fusion with LiBO₂ (ensuring a thorough sample/tracer isotopic equilibration in the molten glass, in case the isotope dilution method is used), or by hydrofluoric acid dissolution. The hafnium fraction separated in this way is ready for isotope ratio measurements by MC-ICP-MS, while the REEs are further processed by extraction chromatography for isolating Nd, Sm, and Lu, in view of TIMS and MC-ICP-MS analyses. The precision and accuracy of the method were evaluated by repeat analyses of four geological Reference Materials covering a range of silicate rock compositions.