A rapid single-column separation of lithium isotopes from diverse matrices for MC-ICP MS analysis

Abstract

Lithium (Li), as a key mineralizing element, is not only of substantial strategic importance but also acts as a powerful tracer for a wide range of geological processes, owing to the large relative mass difference between its two stable isotopes, ⁶Li and ⁷Li. Conventional Li separation methods either use organic solvents that entail health hazards and degrade ion-exchange resins, or rely on AG 50W-X8 or X12 resins in single- or dual-column configurations, which are limited by poor universality, high acid consumption, and laborious procedures. To overcome these drawbacks, this study presents a rapid chemical separation protocol for lithium applicable to a variety of rock matrices. The entire procedure uses 0.2 mol L⁻¹ hydrochloric acid as the eluent under a single elution scheme with 3.0 mL of AGMP-50 resin, enabling simplified operation while effectively suppressing Na breakthrough. The purified Li fractions exhibit high purity (>99.8%) and low procedural blank levels, allowing high-precision isotopic analysis by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) using the standard-sample bracketing (SSB) method. Furthermore, by lowering the sample loading quantity, this protocol can also be used for the isolation and purification of Li from seawater. To assess the reliability of the proposed method, a systematic analysis was performed on eighteen widely used certified reference materials covering a diverse range of lithologies. The results demonstrate that our data are in excellent agreement with published reference values within analytical uncertainties. Collectively, the rapid Li separation protocol developed in this study integrates high efficiency, good reproducibility, and broad applicability, satisfying the demands for high-precision Li isotopic studies in diverse geological samples.