UNNATURAL ISOTOPIC COMPOSITION OF LITHIUM REAGENTS

Isotopic analysis of 39 lithium reagents from several manufacturers in dicates that seven were artificially depleted in Li-6 significantly in excess of the variation found in terrestrial materials. The atomic we ight of lithium in analyzed reagents ranged from 6.939 to 6.996, and d elta(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 label s of these Li-6-depleted regents do not accurately reflect the atomic and (or) molecular weights of these reagents. In 1993, IUPAC issued th e following statement: ''Commercially available Li materials have atom ic 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 s tatement has been found to be incorrect. In two of the 39 samples anal yzed, the atomic weight of Li was in excess of 6.99.