Adsorptive voltammetry of lipoic acid and lipoamide, based on use of a catalytic hydrogen wave.

The adsorptive voltammetry of lipoic acid and lipoamide was investigated with a hanging mercury drop electrode. These compounds produced a catalytic hydrogen wave at - 1.35 V in ammonia buffer solution containing cobalt(II), and the peak current increased with adsorptive accumulation at the electrode. Thus adsorptive voltammetry with the catalytic hydrogen wave could provide a sensitive method for determining trace amounts of lipoic acid and lipoamide. The calibration graphs for both compounds were linear over the range 2-10nM with accumulation for 5 min at -0.6 V, and the detection limit was ca. 0.5nM.