RECENT DEVELOPMENTS IN INDUCTIVELY-COUPLED PLASMA MAGNETIC-SECTOR MULTIPLE COLLECTOR MASS-SPECTROMETRY

This paper describes advances in isotopic measurements that have been made with an inductively coupled plasma source magnetic sector multipl e collector mass spectrometer and presents results of new experiments aimed at further evaluating the instrument's capability. It is shown u sing standard solutions that trace element ratios such as Rb/Sr can be measured precisely without isotope dilution by comparison with refere nce solutions of known composition. Similarly, using a new wide flight tube, Pb isotopic compositions and U/Pb ratios can be accurately meas ured simultaneously without isotope dilution. The effects of deliberat ely including changes in the running conditions (r.f. power) are shown to be significant for measuring trace element ratios but not for mass bias and interference-corrected isotopic compositions. Finally, it is demonstrated that precise and accurate isotopic compositions of eleme nts as refractory as W can be determined relatively easily by solution nebulization and even by direct laser ablation of complex silicates. Spectral interferences in such experiments are negligible. These exper iments serve to highlight the remarkable potential that this new field offers for hitherto difficult isotopic measurements in nuclear, earth , environmental and medical sciences. Isotopic measurements can be mad e that are reproducible at high precision through a range of running c onditions, even in the presence of isobaric interferences. The ability to correct for mass discrimination accurately using a second element of similar mass, the very high sensitivity for elements that are other wise difficult to ionize, the demonstrated capability for laser ablati on work and the ability to measure through a wide mass range simultane ously give this instrument major advantages over other more traditiona l techniques of isotopic measurement.