A new modification of the sample introduction system for Os isotope ratio measurements

Abstract

Here we present a new modification of the sample introduction system aimed at precisely measuring Os isotope ratios. A small glass connector was used to transfer OsO₄ vapor from a Carius tube into a nebulizer. After dissolution of sample in a Carius tube, Os isotopes in the sample were determined simultaneously through in situdistillation without any prior separation procedure. The analytical precision at intermediate precision conditions of measurement was improved through the simultaneous introduction of Os via sparging and the aspiration of a solution containing Ir for mass bias correction. The present method, which involves the passage of Os vapor directly into the ICP-MS torch, thus solves the problems encountered previously when optimizing an instrument. The dating results of reference materials (RMs) HLP and JDC by the modified method are 221.8 ± 0.70 Ma (0.31%, 2s, n = 7) and 140.0 ± 0.44 Ma (0.31%, 2s, n = 9) respectively, which are consistent with their certified values of 221.4 ± 5.6 Ma and 139.6 ± 3.8 Ma respectively. Also reported in this study are dating results of several unknown molybdenite samples by the new method.