Accurate and high-precision measurement of lithium isotopes in two reference materials by MC-ICP-MS

We report here a newly developed method for measurement of Li isotopes by use of multi-collector ICP-MS (Neptune) allowing rapid and high precision determination of Li isotope ratios at low levels of lithium (15-20 ng). The lithium reference sample solution IRMM-016 was analysed over a period of ten months with an external reproducibility of 0.24parts per thousand (2s, n = 52). Chemical separation of Li from matrix was performed on the seawater sample IRMM BCR-403, for which a mean delta(7)Li value of + 31.0 +/- 0. 1parts per thousand (2s/rootn, n = 31) was obtained. This mean value is in good agreement with those previously published for other seawater samples. BCR-403 seawater being readily available, we propose that this seawater sample be used as a reference sample for Li isotope measurements.