Routine Os analysis by isotope dilution-inductively coupled plasma mass spectrometry: OsO4 in water solution gives high sensitivity

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.