Determination of the Isotopic Composition of Gadolinium Using Multicollector Inductively Coupled Plasma Mass Spectrometry

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 Ar(Gd) = 157.2502(6)k=1 were obtained for gadolinium in GADS-1.