The Measurement of the Isotopic Ratios of Rhenium and Osmium of Geological Samples by Negative Ionization Mass Spectrometry

A new method of the measurement of the isotopic ratios of rhenium and osmium by negative ionization mass spectrometry (NTIMS)was developed. In the procedure of Os measurement,first H,Br,Os on the filament was reduced to Os metal in high vacuum, then the mixed solution of Ba (NO3)2 and NaOH was used as an emission auxiliary. Therefore, the lon current was increased to 2 magnitudes. The precision of the main ration was better than 0. 04%. The results of the experiments were corrected for oxygen isotopes according to the equi-probability model. The Re-Os age of Re-Os age reference HLP determined by this method was 223-4±1.5Ma.