A novel chemical purification method for accurate Sn isotope measurement by MC-ICP-MS†

The geological and environmental applications of tin (Sn) isotopes have been hindered by the shortcomings of chemical purification, as severe loss of Sn would occur during sample preparation (evaporation and re-dissolution) and column separation, triggering isotope measurement bias. In this study, we develop a novel and robust separation method to purify Sn from natural samples for accurate isotope measurements. The protocol is established by combining two chromatographic columns loaded with AG 1-X8 and AG 50W-X12 resins, and optimizing the sample evaporation and re-dissolution procedures. The method is proven to efficiently eliminate the main interferents such as Ag, Zn, Mo, Cd and Sb and results in low procedural blank (0.54 ± 0.21 ng, n = 3), quantitative recovery (95–102%, n = 32) and good external precision (δ¹²⁰Sn of 0.02–0.04‰, in 55 measurements) for isotope measurement. The protocol is further applied to seven geological and environmental reference materials (BCR-2, BHVO-2, AGV-2, JG-2, AC-E, PACs-2 and GSS 7) and new values are reported for both odd (δ¹¹⁹Sn and δ¹¹⁷Sn) and even (δ¹²⁰Sn and δ¹²²Sn) Sn isotope ratios. This study demonstrates clearly the potential application of our method for studying the geochemical behaviors of Sn and its isotopes in various aspects.