Isotopic analysis of lithium salts by 6Li nuclear magnetic resonance and Knudsen effusion high temperature mass spectrometry

Reported is a comparative study of the nuclear magnetic resonance (NMR) spectrometric measurement of 6Li with the Knudsen effusion high temperature mass spectrometry (HTMS) determination of 6Li and 7Li. A limit of detection of 0.002–0.007 at.% for 6Li was achieved by NMR with the use of calibrated standard reference materials. This study has shown that 6Li NMR is effective, rapid, and a nondestructive analytical technique for the accurate isotopic analysis of Li salts enriched in 7Li up to 99.95 at.%. The relative standard deviation (RSD) for NMR 6Li determinations in highly enriched Li salts was 0.002–0.007 at.%, when the 6Li content was in the range of 0.05–0.10 at.%. Effusion Knudsen HTMS measurements of samples of various isotopic compositions of highly enriched 7Li lithium salts were completed using mass peaks of Li2Cl+ (m/z=47–51 u). The limit of detection achieved for 6Li in enriched 7Li salts was 0.0002–0.0005 at.% measured with a RSD of 0.015–0.080 at.%. Effusion Knudsen HTMS is an absolute method of analysis requiring no calibration standards.