Acceleration of electroreduction reaction of water-soluble selenium compounds in the presence of methyl viologen

The addition of methyl viologen (MV²⁺) accelerates the reduction of Na₂SeO₃ not only in 0.1 moldm^-3 sodium phosphate buffer (PBS, pH 7) but also in 0.22 moldm^-3 sodium acetate buffer (pH 4). Water-insoluble red Se is dispersed in the vicinity of the electrode surface as the reduced product. Michaelis-Menten-type relationship is obtained between the reduction current and the concentration of Na ₂SeO₃, suggesting that MV²⁺ molecules mediate the electron transfer from the electrode to HSeO3- or SeO₃ ^2- dissolved in PBS. MV²⁺ is also effective in accelerating the reduction of SeO₄^2-, which has already been reported to be electrochemically inactive.