r Toumari - Phase Equilibria Research Laboratory, Department of Chemistry, Faculty of Science, University of Zanjan, Zanjan
h Shayani- Jam - Phase Equilibria Research Laboratory, Department of Chemistry, Faculty of Science, University of Zanjan, Zanjan
M. R. Yaftian - Phase Equilibria Research Laboratory, Department of Chemistry, Faculty of Science, University of Zanjan, Zanjan
m Parinejad - Phase Equilibria Research Laboratory, Department of Chemistry, Faculty of Science, University of Zanjan, Zanjan

The electro-catalytic oxidation of N-acetylcysteine has been studied in presence 4,4'-biphenol, using cyclic voltammetry as a diagnostic technique. Cyclic voltammetry (CV) technique was used to investigate thesuitability of incorporation of 4,4'-biphenol/4,4'-diphenoquinone redox as a mediator [1] for theelectrocatalytic oxidation of N-acetylcysteine in buffered aqueous solution(Phosphate buffer, pH:7). In this work, we described redox couple (4, 4'-biphenol and 4,4'-diphenoquinone) can be used as a suitable mediator for determination of N-acetylcysteine concentration based on the catalytic current (curve b in fig.1). The dependence of peak currents on pH, concentration and the potential scan rate was investigated. Under the optimum conditions the peak current was linear to the concentration of N-acetylcysteine in the range 50-500  in the cyclic voltammetry. The detection limits were determined as 8.3 M by CV method.The diffusion coefficient of N-acetylcysteine and the catalytic rate constant of the reaction of 4,4’-diphenoquinone with N-acetylcysteine based on an EC' mechanism, was estimated using digital simulation method by comparing the experimental cyclic voltammetric responses with the calculated results. [2-3] Finally, the electrocatalytic oxidation of N-acetylcysteine by 4, 4'-diphenoquinone can be employed as a new method for the voltammetric determination of N-acetylcysteine plasma samples.

N-acetylcysteine, Catalytic current, 4, 4'-biphenol, Cyclic voltammetry, Digital simulation, EC' mechanism