Lithium isotope analysis of natural and synthetic glass by laser ablation MC-ICP-MS

This contribution presents the first laser ablation multicollector ICP-MS (LA-MC-ICP-MS) technique for the measurement of Li isotopes. A Nu Instruments NuPlasma HR operating at 6 kV and fitted with a non-standard "low-mass, high abundance'' skimmer cone is used, coupled to a NewWave UP213 213 nm laser ablation unit operating under a He atmosphere. Asymmetric tuning of the quad lenses on the NuPlasma allows the simultaneous measurement of Li-7 and Li-6 on a Faraday-ion counter configuration. Use of the standard-bracketing technique for analysis of unknowns obviates any cross calibration between Faraday cup and ion counter. Use of a natural glass as bracketing standard (e.g. BCR-2G) yields accurate Li isotope data with external, measured 2 sigma delta Li-7 precision of <1 parts per thousand at Li concentrations of 3-35 ppm.