High Precision Measurement of Selenium Isotopic Composition by Hydride Generation Multiple Collector Inductively Coupled Plasma Mass Spectrometry with a 74Se-77Se Double Spike

A method was developed for high precision measurement of selenium isotopes by hydride generator-multiple collector inductively couple plasma mass spectrometer (HG-MC-ICP-MS) using 74Se-77Se double spike and modified thiol-cotton purification. Selenium was separated from the sample matrix using thiol-cotton, and HNO3 + H2O2 separates Se from organic matter in the thiol-cotton that could interfere with hydride generation. The 74Se-77Se double spike corrects for isotope fractionation during purification and mass spectrometry analysis. The external reproducibility for standard NIST SRM3149/MH495 and natural samples were 0.1‰ (2σ) and 0.15‰–0.2‰ (2σ) over the course of several months, respectively. Based on the average yield (85%) of Se separation using thiol-cotton, the minimum quantity of Se for isotope analysis was approximately 20 ng. The results of an interlaboratory standard, MH495, δ82/76SRM3149 = (–3.44 ± 0.1)‰ (2σ), are in good agreement with previously published data δ82/76MH495 VS SRM3149 = (–3.04 ± 0.5)‰ that used a sample-standard bracketing technique. Selenium isotopes were measured in several sedimentary samples with a range from −13.53‰ to 9.03‰ relative to NIST SRM3149. These results suggest a potentially wide application of Se isotopes in environmental, geological, agricultural, and life sciences fields.