Abatrac-The electroreduction of camphorquinone, CQ, at mercury and platinum electrodes was studied by linear-sweep cyclic voltammetry, polarography and double-potential pulse chronowulometry using ACN and buffered aqueous solutions as solvents.
In ACN, the process appears to be. quasi-reversible and involve a single electron; however, it yields no pre-or post-peaks.
In buffered aqueous solutions, a pre-peak system is obtained by cyclic voltammetry at CQ concentrations above 5 x 10m4M. The influence of pH, the CQ concentration and scan rate was studied. Tafel slopes and reaction orders were obtained from the i-E curves traced at potentials corresponding to the foot of the pohuographic wave. The process occurring at the potentials corresponding to the limiting current of the main reduction wave involves two electrons and is diffusion-controlled at low CQ concentrations. In acid media, the reduction pathway is an ECE mechanism whose rate-determining step (RDS) is the protonation of the radical anion formed after the first electron transfer. In basic media, the irreversible second one-electron transfer is the RDS.
The diffusion coeflicient of CQ was determined in the two assayed solvents. The relatively high coefllcient obtained in aqueos solutions is discussed.