Submicrosecond spectroelectrochemistry applied to chlorpromazine cation radical charge transfer reactions

A beam of light reflected from a 50–400 μm diameter disk electrode was used to monitor the concentration of an electrogenerated absorber in the submicrosecond time scale. The electrode potential was established in less than 1 μs after a potential step, and charge injection further reduced this response time to less than 40 ns. Absorbance measurements agreed with theory for planar diffusion from 150 ns to 100 ms, at which point nonlinear diffusion caused a negative deviation from planar behavior. The technique was used to monitor the kinetics of the oxidation of dopamine by electrogenerated chlorpromazine cation radical. The method was used to monitor this process in the physiological pH region, where the reaction is too fast for stopped-flow techniques.