A fast double-stack column chemical separation of Zn and Mo from geological samples for isotopic analysis by MC-ICP-MS

Abstract

A time-saving and highly efficient chemical separation procedure to isolate Zn and Mo from various geological samples is developed, which is based on a single pass of a double-stack column. The first column, filled with AG MP-1M resin (100–200 mesh, Bio-Rad), quantitatively removed matrix and interference elements from sample matrices; while the second column, filled with the DGA spec resin (50–100 μm, Eichrom), further isolated Zn and Mo from sample matrices. The proposed protocol was time-saving (50% column running time) and afforded efficient separation and quantitative recovery (more than 96% and 92% for Zn and Mo, respectively) from complex sample matrices of three geological reference materials W-2a, GSR-1 and GSR-2. Both Zn and Mo isotope ratios in the purified Zn and Mo solutions were determined by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) with the use of the combined standard-sample bracketing and internal normalization (C-SSBIN) method and double-spike method, respectively, for mass bias correction. In addition, the effects of two cone combinations and three mass bias correction methods on Zn isotopic analysis were investigated. The results show that the jet + X cone and the C-SSBIN method with Cu as the internal standard provided high accuracy and precision Zn isotope ratio measurements. Zn and Mo isotope ratios were measured in thirteen geological reference materials for the validation of the feasibility and effectiveness of the proposed method with satisfactory results in this study.