In Situ Determination of First-Row Transition Metal, Ga and Ge Abundances in Geological Materials via Medium-Resolution LA-ICP-MS

An in situ, medium-resolution LA-ICP-MS method was developed to measure the abundances of the first-row transition metals, Ga and Ge in a suite of geological materials, namely the MPI-DING reference glasses. The analytical protocol established here hinged on maximising the ablation rate of the ultraviolet (UV) laser system and the sensitivity of the ICP-MS, as well minimising the production of diatomic oxides and argides, which serve as the dominant sources of isobaric interferences. Non-spectral matrix effects were accounted for by using multiple external calibrators, including NIST SRM 610 and the USGS basaltic glasses BHVO-2G, BIR-1G and BCR-2G, and utilising 43Ca as an internal standard. Analyses of the MPI-DING reference glasses, which represent geological matrices ranging from basaltic to rhyolitic in composition, included measurements of concentrations as low as < 100 mu g g-1 and as high as > 104 mu g g-1. The new data reported here were found to statistically correlate with the 'preferred' reference values for these materials at the 95% confidence level, though with significantly better precision, typically on the order of < 3% (2s(m)). This analytical method may be extended to any matrix-matched geological sample, particularly oceanic basalts, silicate minerals and meteoritic materials.