Synthesis of New 14- and 15-Crown-Formazans and their Evaluation in Spectrophotometric Determination of Lithium

The two new crown-formazans 1 and 2 with 14-and 15-membered rings have been synthesized, characterized and investigated as a selective spectrophotometric chelating agents for lithium. The effect of sodium ion concentration on the background lithium signal was studied. Sodium causes depression of the lithium signal and the relative effect diminishes as the total sodium concentration is increased. In a background sodium containing 140 mM sodium, a 10 mM increment of sodium is equivalent to 0.0017 mM Lithium using compound 1 and 0.0024 mM using compound 2.