Analytical Capability of High-Time Resolution-Multiple Collector-Inductively Coupled Plasma-Mass Spectrometry for the Elemental and Isotopic Analysis of Metal Nanoparticles

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We measured the Re/Os (¹⁸⁵Re/¹⁸⁸Os) and ¹⁸⁷Os/¹⁸⁸Os ratios from nanoparticles (NPs) using a multiple collector-inductively coupled plasma-mass spectrometer equipped with high-time resolution ion counters (HTR-MC-ICP-MS). Using the HTR-MC-ICP-MS system developed in this study, the simultaneous data acquisition of four isotopes was possible with a time resolution of up to 10 μs. This permits the quantitative analysis of four isotopes to be carried out from transient signals (e.g., <0.6 ms) emanating from the NPs. Iridium–Osmium NPs were produced from a naturally occurring Ir–Os alloy (ruthenosmiridium from Hokkaido, Japan; osmiridium from British Columbia, Canada; iridosmine from the Urals region of Russia) through a laser ablation technique, and the resulting nanoparticles were collected by bubbling water through a suspension. The ¹⁸⁷Os/¹⁸⁸Os ratios for individual NPs varied significantly, mainly due to the counting statistics of the ¹⁸⁷Os and ¹⁸⁸Os signals. Despite the large variation in the measured ratios, the resulting ¹⁸⁷Os/¹⁸⁸Os ratios for three Ir–Os bearing minerals, were 0.121±0.013 for Hokkaido, 0.110±0.012 for British Columbia, and 0.122±0.020 for the Urals, and these values were in agreement with the ratios obtained by the conventional laser ablation-MC-ICP-MS technique. The data obtained here provides a clear demonstration that the HTR-MC-ICP-MS technique can become a powerful tool for monitoring elemental and isotope ratios from NPs of multiple components.