Testing miniaturized extraction chromatography protocols for combined 87Sr/86Sr and δ88/86Sr analyses of pore water by MC-ICP-MS

We tested two miniaturized extraction chromatography protocols for strontium isolation based on 300 mu L (Protocol 1) and 30 mu L (Protocol 2) column volumes of Sr-Spec resin, for the simultaneous determination of Sr-87/Sr-86 and delta Sr-88/86 by MC-ICP-MS. The accuracy and precision of the Sr isotope ratios have been evaluated by analyzing JCt-1 and SRM 1640a reference materials, resulting in a reproducibility of Sr-87/Sr-86 and delta Sr-88/86 values of 0.000026 and 0.04 parts per thousand (Protocol 1) (2SD, n = 3), and of 0.000074 and 0.13 parts per thousand (Protocol 2) (2SD, n = 4), respectively. The Sr isotopic composition of SRM 1640a, presented here for the first time, is Sr-87/Sr-86 = 0.708790 +/- 0.000062 and delta Sr-88/86 = 0.07 +/- 0.10 parts per thousand (2SD, n = 6). Protocols 1 and 2 were successfully applied to pore waters extracted from marine sediment cores from the northern Barents Sea. Our results demonstrate that both protocols attain accurate Sr-87/Sr-86 ratios and allow the detection of natural variations in delta Sr-88/86 in marine pore waters. Compared to previous Sr/matrix separation methods, Protocol 2 is significantly less costly, making it particularly suitable for large-scale oceanological and limnological studies.

Automated summary

Two miniaturized extraction chromatography protocols were tested for strontium isolation, both of which accurately determined Sr isotope ratios and allowed the detection of natural variations in marine pore waters. Protocol 2, with significantly lower cost compared to previous methods, is particularly suitable for large-scale oceanological and limnological studies.