Removal of Isobaric Interferences by Resonance Ionization Mass Spectrometry

The technique of resonance ionization mass spectrometry (RIMS) has been successfully applied to the measurement of isotope ratios for several elements. In the case of neodymium and samarium, isobaric interference was removed at isotopic masses 144, 148 and 150. Isotope ratios were measured for these two elements in an equimolar mixture, with a significant improvement in accuracy compared to conventional thermal ionization mass spectrom-etry. In addition, RIMS was applied to the elements uranium and plutonium in order to eliminate isobaric interferences at mass 238 and potentially at mass 241 (due to americium). Recent results are presented for measurements made on nanogram size samples loaded on resin beads.