High precision measurements of lithium isotopic composition at sub-nanogram by MC-ICP-MS with membrane desolvation

The geochemistry of Li and Li isotopes is a promising tracer of chemical weathering processes for both modern and ancient times. Therefore, accurate and precise determination of the isotopic composition of Li is required for a large variety of complex geological samples with different Li concentrations and matrix/Li ratios. Especially, geochemical studies of precious geological samples with ultra-low lithium content and high matrix. In this study, the accuracy and the precision corresponding to Li isotopic measurements of low-level samples using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) with membrane desolvation introduction system was evaluated. The method of MC-ICP-MS with membrane desolvation and a high-sensitivity X-skimmer cone, together with a simple one-step column separation enabled the high-precision isotopic analysis of Li quantities as small as 2 ng. The long-term instrumental external reproducibility of delta 7Li values for the L-SVEC and SPEX-Li were 0.0 +/- 0.1 parts per thousand (n = 20) and 12.1 +/- 0.4 parts per thousand (n = 20), respectively. Based on the measurements on a series of international reference materials over the last two years. The measured delta 7Li values for the standards with a variety of matrices, including BHVO-2, AGV-2 and seawater (NASS-6). The delta 7Li values of BHVO-2 (4.58 +/- 0.35 parts per thousand), AGV-2 (6.85 +/- 0.40 parts per thousand) and NASS-6 (30.88 +/- 0.20 parts per thousand) are in agreement with the published data within the uncertainty. We also present analytical results for South China Sea surface seawater water, meteorite, limestones and rain water. These results demonstrate the validity of the method for obtaining highly precise and accurate outcomes. The delta 7Li measured with different sample sizes and different introduction system ("Wet plasma" and "Dry plasma").