A simplified dual-column system for Li purification and isotopic analysis of geological materials by MC-ICP-MS

Lithium (Li) isotopes have been widely used to investigate continental weathering, climate change, recycling of surface materials and ore formation. However, muti-column systems and/or a large volume of eluents are generally required for Li purification and its accurate isotopic measurements due to variably high matrix/Li ratios of different geological materials. Here we present a simplified dual-column system with small volumes of resins (3 mL + 2 mL) and eluents (16 mL 0.5 M HCl + 22 mL 0.2 M HCl) for Li purification of various geological materials. This system can efficiently separate Li from matrix elements with a very low blank level (∼25 pg), high yield (99.3%-99.8 %) and narrow Li collection ranges (10 mL in each column stage). Additionally, we first demonstrate that the largest total cation content of loaded samples can be up to 24.4 % of the resin (AG 50W-X8) capacity for Li purification. The effects of acid and Li concentration mismatch, solution Li concentration and matrix elements on the accuracy and precision of Li isotopic analysis are also systematically evaluated for the new generation of dual-path MC-ICP-MS (Nu Sapphire). The reliability of the new procedure for Li purification and isotopic analysis is confirmed by analyzing twelve international geological reference materials (including ten mafic to felsic silicate igneous rocks, a meta-sediment (SDC-1) and a carbonatite (COQ-1)) and results obtained are consistent with previously reported data with a long-term reproducibility better than 0.20 ‰ (2SD). Therefore, our study provides a simplified and efficient system for Li purification and isotopic analysis by MC-ICP-MS.