Rapid Separation and Precise Determination of Strontium Isotopic from Geological Samples with High Rubidium/Strontium Ratios

In the isotopic measurement of strontium (Sr) of geological samples with high rubidium (Rb)/Sr ratios, it is difficult to completely remove the isobaric interference of Rb on Sr isotopic analysis by a single separation and purification using traditional strong acid cation exchange resin. Actually, one purification procedure performed twice is necessary to eliminate the interference of 87Rb on the testing of 87Sr/86Sr. Although the purification procedure can ensure a good effect on the separation and purification of Sr, the process is tedious and time-consuming, which is not suitable for simultaneous separation and purification of Sr from large quantity of geological samples with high Rb/Sr ratios. In this study, the conventional two-stage separation process was optimized, and an experimental method for rapid separation of Sr from geological samples with high Rb/Sr ratios was established. In this method, the Sr solution after purified by AG50 resin was directly added to a new AG50 resin to purify Rb and Sr again. The whole separation process would be accomplished quickly and efficiently. The method combined with highly sensitive thermal ionization mass spectrometer (TIMS) technique was completely satisfied in high precision determination of 87Sr/86Sr isotope ratio in the samples with high Rb/Sr ratios. Through the application of the novel separation method with a large number of geological samples with high Rb/Sr ratios, it was proved that the experimental process was stable and reliable and showed crucial application value.