Reaction between l-cysteine and 10-methylphenothiazine cation radical released from droplet-modified electrodes

The electrochemical oxidation of 10-methylphenothiazine (PMe) dissolved in 1,2-trans-dibromocyclohexane oil droplets immobilised on a basal plane pyrolytic graphite (BPPG) electrode and bathed by an aqueous electrolyte is a one-electron quasi-reversible process which occurs with the expulsion of the electro-generated cation radical from the oil phase. In the presence of l-cysteine in the aqueous phase, the electro-released cation mediates the redox catalytic oxidation of the thiol. The peak catalytic current is observed to increase linearly with increasing cysteine concentration over the range analysed (10–100 mM).