Formation of a Keggin-type 12-molybdogallate(III) complex in aqueous-organic media and the application to the voltammetric determination of gallium(III)

A simple method has been developed for the voltammetric determination of Ga (III). In a 50 mM Mo(VI)-0.2 M HCl-40%(v/v) CH3CN system, Ga(III) reacts di rectly with Mo(VI) to form a 12-molybdogallate(III) complex. The yellow Keg gin complex undergoes a two-step reduction to the mixed-valence heteropoly- blue species at the glassy carbon (GC) electrode. The 1st voltammetric redu ction current depends linearly on the Ga(III) concentration in the range of 5x10(-5)- 1x10(-3) M. Common metal ions including AI(III) and In(III) at 1 00-fold concentrations caused no interference. The effect of organic solven ts on the formation of the Keggin complexes prepared so far is also discuss ed.