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 s table and the latter gives 30 times higher sensitivity than the former for ICP-MS analysis. The use of an offline OsO4 generator can effectively conve rt osmium to Os(VIII) and allows thorough cleaning after each sample prepar ation. The instrument memory for Os can be effectively cleaned by alternate ly 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 s ample preparation and long equilibrium time for Os analysis by ICP-MS, an i sotope dilution (ID) method was adopted in this study. The ID-ICP-MS techni que 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 ha s been applied to a series of eight Chinese national standard reference mat erials, ranging from soil, sediments, peridotite, to sulfide. The results a re in good agreement with the certified values. The method precision is bet ter than 6% RSD.