Selective Oxidation of Thiols to Disulfides at Polymeric Cobalt Phthalocyanine Chemically Modified Electrodes

Abstract

Cysteine, glutathione, and several other aliphatic and aromatic thiols were exhaustively oxidized at chemically modified reticulated vitreous 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 nuclear magnetic resonance spectrometry confirmed that, for cysteine and glutathione, the corresponding disulfide species were formed very cleanly with no evidence of further oxidation to the sulfinic or sulfonic acid. The polymeric CoPC electrodes were compatible with a wide range of solvent and pH conditions. Unlike most conventional electrodes, which are rapidly passivated upon attempted oxidation of organosulfur compounds, the CoPC electrodes were extraordinarily durable, exhibiting turnover numbers of greater than 10⁴ for each center with little or no loss of activity.