Determination of natural isotopic variation in nickel using inductively coupled plasma mass spectrometry

In this study, we measured natural isotopic variation of terrestrial nickel using multiple-collector inductively coupled plasma mass spectrometry. External precisions in 58Ni/62Ni, 60Ni/62Ni, 61Ni/62Ni, and 64Ni/62Ni ratios of 0.02%, 0.01%, 0.04%, and 0.09% (2 × standard deviation), respectively, were routinely obtainable for a Ni isotopic reference standard by correcting the mass discrimination effect with a 65Cu/63Cu ratio of 0.4456. Only a small isotopic variation of ±0.15‰ amu−1 was observed among seven commercially available reagent-grade nickel metals, while variation of ±0.20‰ amu−1 was observed for two nickel sulfide samples from Canada. The isotopic compositions of the two types of samples overlap. The overall variation of ±0.25‰ amu−1 corresponds to an uncertainty of 0.000 37 for the atomic weight of nickel; this uncertainty is twice the currently recommended value (56.6934 ± 0.0002) for the standard atomic weight of terrestrial nickel as proposed by IUPAC.