Progress in multi-ion counting spark-source mass spectrometry (MIC-SSMS) for the analysis of geological samples

Spark source mass spectrometry (SSMS) has experienced important and signifi cant improvements in nearly all analytical features by the use of a multipl e ion counting (MIC) system. Two procedures have recently been developed to further increase the analytical capabilities of MIC-SSMS in geochemistry. These are a mathematical correction of interferences, which is often necess ary for the ultra trace element analysis of Nb, Ta, Zr, Hf and Y, and the d evelopment of an autospark system to hold the total ion beam constant. New analytical data for geological samples, especially international refere nce materials, are presented using the improved MIC-SSMS technique. The dat a set consists of high precision and low abundance data for Zr, Nb and Y in depleted reference materials. The MIC-SSMS results are compared with those of conventional SSMS using photoplates for ion detection. The precision of the MIC-SSMS isotope ratio measurements (about 1%) is more than a factor o f 3 better than that of conventional SSMS, as demonstrated by analyses of H awaiian samples. Total uncertainties of MIC-SSMS concentration data includi ng all sources of error are generally between 2 and 5% for concentrations h igher than about 0.3 mug/g and about 10% for trace element abundances in th e ng/g range.