A simple single-stage extraction method for Mo separation from geological samples for isotopic analysis by MC-ICP-MS

Abstract

A new, simple and efficient separation method to isolate Mo from complex geological sample matrices for high precision Mo isotope ratio measurements is described. The proposed separation method benefits from the high selectivity and high capacity of the TRU resin, which affords straightforward separation of Mo from complex sample matrices and achieves high yield (∼100%), efficient separation and low blank with the use of only a single mineral acid, HCl (1.5 M for loading and 0.5 M for eluting), and small volumes. As opposed to the commonly used separation protocols, neither redox reagents (e.g., H₂O₂ and ascorbic acid) nor highly toxic HF is required for the proposed separation protocol, making this separation method straightforward and more environment friendly to operate. Mo isotope ratios were measured by multi-collector inductively coupled plasma mass-spectrometry (MC-ICP-MS) using the ⁹⁷Mo–¹⁰⁰Mo double spike in combination with standard-sample bracketing for mass bias correction. The results obtained for igneous rocks, manganese nodules, shales and seawater samples are in good agreement with previously reported values, confirming that the proposed separation protocol is suitable for complex sample matrices and will further promote its geological applications.