| Abstract | In this study, we report independent measurements of all stable isotope ratios of gadolinium. Our study employs multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) with National Research Council Canada (NRC) HALF-1 isotopic hafnium standard as a primary calibrator and surveys four commercial gadolinium materials, including a NRC candidate isotopic reference material, GADS-1. The isotopic composition of gadolinium is determined using the regression model without reliance on conventional normalizing isotope ratios or mass-dependent isotope ratio correction models. In this work, all gadolinium isotope ratios were obtained from ¹⁶⁰Gd/¹⁵⁸Gd which, in turn, was measured from hafnium ¹⁷⁸Hf/¹⁷⁷Hf either directly or indirectly through ¹⁶⁷Er/¹⁶⁶Er. The latter approach was used for the final determination of gadolinium isotopic composition, as it provides smaller combined uncertainty. We report high-precision measurements of the isotopic composition of gadolinium, which support a revised standard atomic weight. Isotope amount ratios of R₁₅₂/₁₅₈ = 0.008 20(2) ₖ₌₁, R₁₅₄/₁₅₈ = 0.087 98(12) ₖ₌₁, R₁₅₅/₁₅₈= 0.596 81(63) ₖ₌₁, R₁₅₆/₁₅₈ = 0.825 08(57) ₖ₌₁, R₁₅₇/₁₅₈ = 0.630 60(22) ₖ₌₁, and R₁₆₀/₁₅₈ = 0.879 10(60) ₖ₌₁, and the atomic weight of A ᵣ(Gd) = 157.2502(6) ₖ₌₁ were obtained for gadolinium in GADS-1. |
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