Rapid determination of V isotopes with MC-ICP-MS: new developments in sample purification

Abstract

Vanadium (V) isotopes are a powerful tool for fingerprinting the redox-state variations in geological processes, but their widespread application is hindered by the complicated processes of separation of V from matrix elements. In this study, we established a two-stage chromatography technique using cation and anion exchange resins for V purification from natural samples. This method can quantitatively and efficiently separate V from matrix elements, especially Ti and Cr, which introduce spectral interferences. The V isotopic composition was analysed using multi-collector inductively coupled plasma-mass spectrometry. The instrumental mass fractionation of V isotopic ratios was corrected by the sample-standard-bracketing method. The δ⁵¹V values of two in-house standard solutions, CUG-V and BDH-V, were 0.04 ± 0.08‰ (2 SD, n = 121) and −1.23 ± 0.08‰ (2 SD, n = 91), respectively. The V isotope compositions of 13 reference materials, including igneous rock, manganese nodules, carbonaceous siliceous shale, sediment and soil, were measured in this study. Based on the repeated measurements of pure solution and reference materials, the long-term reproducibility was better than ± 0.10‰ (2 SD) for δ⁵¹V values. The new approach to V isotope analysis presented in this work is both economical and time-efficient, improving the ability for further investigation of V isotope geochemistry in various geological and environmental systems.