Abstract
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) produced by 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.
