| Abstract | In this study, we report the first independent measurements of lutetium isotopic composition using multi-collector ICPMS in four commercial lutetium materials, including a new NRC candidate lutetium isotopic reference material, LUIS-1. The regression model was used to correct for the instrumental isotopic fractionation (mass bias) using NIST SRM 989 isotopic rhenium as the primary calibrator. The regression model is based on a short 15-min measurement sessions at varying ICP plasma power. Isotope ratio of R₁₇₆/₁₇₅ = 0.026553(11)ₖ₌₁, corresponding isotopic abundances of x₁₇₆ = 0.025866(11)ₖ₌₁, x₁₇₅ = 0.974134(11)ₖ₌₁, and an atomic weight of Aᵣ(Lu) = 174.966693(13)ₖ₌₁ were obtained for lutetium in LUIS-1. Uncertainty estimation was performed using a mixture of modeling approaches in accordance with the JCGM 100:2008 “Guide to the Expression of Uncertainty in Measurement” and its Supplement 1. The relative contribution of the rhenium primary standard to the combined uncertainty of ¹⁷⁶Lu/¹⁷⁵Lu isotope ratio was 15%. |
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