Abstract

Os(IV) in 5% HCl + 5% ethanol solution and Os(VIII) in water solution are stable and the latter gives 30 times higher sensitivity than the former for ICP-MS analysis. The use of an offline OsO₄ generator can effectively convert osmium to Os(VIII) and allows thorough cleaning after each sample preparation. The instrument memory for Os can be effectively cleaned by alternately flushing with 30% H₂O₂ and 5% HNO₃ for 10 min. In order to overcome the analytical difficulties such as possible loss of the volatile OsO₄ during sample preparation and long equilibrium time for Os analysis by ICP-MS, an isotope dilution (ID) method was adopted in this study. The ID-ICP-MS technique enables us to measure samples with Os content as low as 0.03 ng g⁻¹, after Os is converted to OsO₄ and trapped in water solution. This method has been applied to a series of eight Chinese national standard reference materials, ranging from soil, sediments, peridotite, to sulfide. The results are in good agreement with the certified values. The method precision is better than 6% RSD.