Rapid separation scheme of Sr, Nd, Pb, and Hf from a single rock digest using a tandem chromatography column prior to isotope ratio measurements by mass spectrometry

A straightforward tandem column separation procedure is presented for the separation of Sr, Nd, Pb, and Hf from silicate materials. It allows rapid purification, without any intervening evaporation, of these four elements of great interest in Earth science and cosmochemistry. After sample loading, the upper Sr Spec column adsorbs Sr and Pb, while the lower TODGA Spec column adsorbs Hf and Nd. Strontium-lead and hafniumneodymium elements are then back-extracted from the Sr Spec and TODGA Spec columns, respectively. The whole separation procedure, including column setup, cleaning, and pre-conditioning, takes approximately eight hours for separating a batch of 25 samples. The proposed procedure offers significant improvement in separation efficiency of these often-used four elements, compared with conventional four column methods. Fractions of Sr, Nd and Pb are then measured by TIMS and the Hf fraction is determined by MC-ICP-MS. The stability of this procedure was demonstrated by replicate measurements of Sr-87/Sr-86, Nd-143/Nd-144, Hf-176/Hf-177, Pb-206/Pb-204, Pb-207/Pb-204 and Pb-208/Pb-204 isotope ratios of eight international silicate rock reference materials, spanning a wide range of bulk compositions. The analytical results obtained in this study agree well with published data. The external reproducibility (2RSD, n = 8) of standard BCR-2 was +/-0.0026% for 87Sr/86Sr, +/-0.0020% for 143Nd/144Nd, +/-0.0049% for 176Hf/177Hf, and +/-0.0260.034% for 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb isotope ratios.