SELECTIVE OXIDATION OF THIOLS TO DISULFIDES AT POLYMERIC COBALT PHTHALOCYANINE CHEMICALLY-MODIFIED ELECTRODES

Cysteine, glutathione, and several other aliphatic and aromatic thiols were exhaustively oxidized at chemically modified reticulated vitreou s carbon containing a polymer coating of cobalt phthalocyanine (CoPC). Coulometric measurements indicated that, for all thiols examined, the electro-oxidation was a one-electron process. Subsequent end product analysis by high performance liquid chromatography, polarimetry, and C -13 nuclear magnetic resonance spectrometry confirmed that, for cystei ne and glutathione, the corresponding disulfide species were formed ve ry cleanly with no evidence of further oxidation to the sulfinic or su lfonic acid. The polymeric CoPC electrodes were compatible with a wide range of solvent and pH conditions. Unlike most conventional electrod es, which are rapidly passivated upon attempted oxidation of organosul fur compounds, the CoPC electrodes were extraordinarily durable, exhib iting turnover numbers of greater than 10(4) for each Co2+ center with little or no loss of activity.