An extraction chromatography method for Hf separation prior to isotopic analysis using multiple collection ICP-mass spectrometry

A novel method for the single-step separation of Zr + Hf from all matrix el ements of geological samples has been developed for Hf isotopic measurement s using multiple collector-ICP-mass spectrometry, The method combines an ef fective sample decomposition by LiBO2 fusion with a selective separation of Hf + Zr by a solid-phase extraction material based on dipentyl pentyl phos phonate, commercially available as U-TEVA.Spec. Using this simple and rapid procedure, Hf and Zr can be isolated in a single separation step with good recoveries (> 90%) and satisfactory blank levels (similar to 55 pg of Hf), so that a subsequent isotopic measurement with ICPMS is possible. An excel lent separation from rock-forming constituents is achieved, including those elements (Al, P, Ti, Cr, Fe, Mo, etc.) known to interfere in conventional separation methods based on ion-exchange techniques. The potential of this new method for Hf isotopic analysis is demonstrated by replicate MC-ICPMS m easurements of Hf-176/Hf-177 ratios in seven international reference materi als of silicate rocks, spanning a range of Hf contents and bulk composition s.