Three secondary reference materials for lithium isotope measurements: Li7-N, Li6-N and LiCl-N solutions

The CRPG (Nancy, France) has prepared secondary reference materials for Li isotope measurements by mixing Li-7 or Li-6 spikes and either L-SVEC or IRMM-016 certified reference materials to produce solutions having a known Li concentration and isotopic composition. The Li7-N and Li6-N solution samples (1.5 mol I-1 HNO3) have nominal delta Li-7 isotopic compositions of 30.1 %0 and -9.7%0 respectively relative to L-SVEC and concentrations of 100 mg I-1. Repeated measurement of these samples using the QUAD-ICP-MS at the CRPG yielded delta Li-7 of 30.4 +/- 1.1 %0 (n = 13) and -8.9 +/- 0.9%0 (n = 9) at the 2s level of confidence. An additional LiCl-N solution was measured and yielded a delta value of 9.5 +/- 0.6%0 (n = 3). Identical results were obtained at the BRGM (Orleans, France) from determinations performed with a Neptune MC-ICP-MS (30.2 +/- 0.3%0, n = 89 for the Li7-N, -8.0 +/- 0.3%0, n = 38 for the Li6-N and 10.1 +/- 0.2%0, n = 46 for LiCl-N at the 2s level of confidence). The deviation of measured composition relative to the nominal value for the Li6N solution might be explained by either contamination during preparation or an error during sample weighing. These secondary reference materials, previously passed through ion exchange resin or directly analysed, may be used for checking the accuracy of Li isotopic measurements over a range of almost 40%0 and will be available to the scientific community upon request to J. Carignan or N. Vigier, CRPG.