Determination of molybdenum in nickel-base heat-resisting alloys by isotope dilution mass spectrometry

Molybdenum contents of 3 to 9 wt percents in several analytical standard materials, mainly nickel-base heat-resisting alloys (JAERI and NBS), were determined by isotope dilution mass spectrometry. The technique involved acids-digestion of a chipped sample and addition of a 96 atomic percent Mo-96 spike solution into aliquoted sample solutions prior to isotope analysis. A carbonization technique was applied in single filament surface ionization mass spectrometry in order to make molybdenum isotope ratio measurements simple and reproducible. Except for the samples containing niobium and/or zirconium, the method was capable of obtaining molybdenum contents with relative standard deviations of 0.5 to 1 percent, without separation of element from the matrix. For the samples contained niobium and/or zirconium, it is preferable to separate them by precipitation of molybdenum with alpha -benzoinoxime in order to shorten the overall analysis time. (author)