Abstract
A simple voltammetric method has been developed for the determination of V(V) and V(IV). When a mixture of V(V) and V(IV) is added last of all to a 50 mM Mo(VI)-0.3 M HCl-70%(v/v) CH3CN system, only V(V) reacts with Mo(VI) to form a 12-molybdovanadate(V) complex which undergoes a two-step reduction at the glassy carbon (GC) electrode; the reduction current is directly proportional to the V(V) concentration in the mixture. On the other hand, when HCl is added last after heating the Mo(VI)-CH3CN system containing a mixture of V(V) and V(IV) at 60°C for 10 min, V(IV) is com-pletely oxidized to V(V), and the total concentration of vanadium is determined. The V(IV) concentration is determined by subtracting the V(V) concentration before oxidation from the total concentration of vanadium. Interferences from foreign ions are also discussed.
