Unnatural isotopic composition of lithium reagents

Isotopic analysis of 39 lithium reagents from several manufacturers indicates that seven were artificially depleted in Li-6 significantly in excess of the variation found in terrestrial materials. The atomic weight of lithium in analyzed reagents ranged from 6.939 to 6.996, and delta(7)-Li, reported relative to L-SVEC lithium carbonate, ranged from -11 to +3013 parts per thousand. This investigation indicates that Li-6-depleted reagents are now found on chemists' shelves, and the labels of these Li-6-depleted regents do not accurately reflect the atomic and (or) molecular weights of these reagents. In 1993, IUPAC issued the following statement: ''Commercially available Li materials have atomic weights that range between 6.94 and 6.99; if a more accurate value is required, it must be determined for the specific material.'' This statement has been found to be incorrect. In two of the 39 samples analyzed, the atomic weight of Li was in excess of 6.99.