Voltammetric Determination of Cysteine by Means of 4 4 - biphenol as a Homogeneous Mediator

Cysteine (2-amino-3-mercaptopropanoic acid, CySH) is a type of the important amino acids which is widespread used in the medicine and food additives. It is important in collagen production, as well as skin elasticity and texture [1]. In recent years, several analytical approaches have been reported for electrocatalytic oxidation of 4,4 -biphenol toward the determination of thiols in the literature[2,3]. In this research 4,4 -biphenol was used as a homogeneous mediator for determination of cysteine, on glassy carbon. Cyclic voltammetry and liner sweep voltammetry were applied for describing the electrochemical properties of 4,4 -biphenol and to investigate its electrocatalytic effect on the cysteine oxidation. The results indicated that 4,4 -biphenol remarkably accelerate the electron transfer reactions of cysteine.The diffusion coefficient of cysteine and the catalytic rate constant of the reaction of 4,4 -diphenoquinone with cysteine was also estimated using chronoamperometry method. The proposed method was successfully used for the determination of cysteine in serum samples.