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 μL (Protocol 1) and 30 μL (Protocol 2) column volumes of Sr-Spec resin, for the simultaneous determination of 87Sr/86Sr and δ88/86Sr 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 87Sr/86Sr and δ88/86Sr values of 0.000026 and 0.04‰ (Protocol 1) (2SD, n = 3), and of 0.000074 and 0.13‰ (Protocol 2) (2SD, n = 4), respectively. The Sr isotopic composition of SRM 1640a, presented here for the first time, is 87Sr/86Sr = 0.708790 ± 0.000062 and δ88/86Sr = 0.07 ± 0.10‰ (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 87Sr/86Sr ratios and allow the detection of natural variations in δ88/86Sr 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.