High-precision simultaneous determination of ~(147)Sm/~(144)Nd and Nd/ ~(144)Nd ratios in Sm-Nd mixtures using multi-collector inductively coupled plasma mass spectrometry and its comparison to isotope dilution analysis

摘要

This work demonstrates, for the first time, the feasibility and capability of the high-precision simultaneous determination of ~(147)Sm/~(144)Nd and ~(143)Nd/~(144)Nd ratios in Sm-Nd mixtures using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) without Nd and Sm separation and without the use of costly enriched spikes. Mass discrimination was exponentially corrected by applying the natural constant of ~(146)Nd/ ~(144)Nd ratio as an internal standard, after correction of the isdbaric interference of ~(144)Sm on ~(144)Nd using interference-free ~(147)Sm/~(149)Sm ratio for Sm mass fractionation, without assuming identical mass bias of Nd and Sm. The accuracy and precision of the present protocol, obtained from replicate analyses of various types of Sm-Nd mixtures encompassing a wide range of Sm/Nd (ca. 0.1-1.0) or ~(147)Sm/~(144)Nd ratios (ca. 0.06-0.62) was found to be comparable to the classic isotope dilution (ID) method. The present method is characterized by a higher sample throughput compared to the ID method, and shows great potential for the simultaneous determination of ~(147)Sm/~(144)Nd and ~(143)Nd/~(144)Nd ratios in real geological samples.