Electrocatalytic oxidation of sulfhydryl compounds at ruthenium(III) diphenyldithiocarbamate modified carbon paste electrode

An aqueous insoluble new redox mediator ruthenium(III)-diphenyldithiocarbamate has been used as a modi her to prepare a carbon paste electrode. The modified electrode was characterized by cyclic voltammetry by varying the pH of the medium and also the scan late. The electrode was scanned between 0.0 V and +0.8 V in 0.1 M KNO3 medium. Anodic and cathodic peaks were observed at +0.38 V and +0.22 V, respectively, for a scan rate of 100 mV/s. The modified electrode is found to oxidize electrocatalytically cysteine and glutathione. Conditions such as pH and scan rate have been optimized for the determination of both compounds. Linear response for cysteine is in the ranee of 0.00-15.20 mg/L, with a correlation coefficient (r), of 0.9992. Standard deviation for 10 repetitive determinations was found to be 0.0756. The linear range for glutathione is 0.00-30.40 mg/L, with a value of 0.9995 for r, and the standard deviation is 0.1449. The stability and reproducibility of the electrode for the determination of cysteine and glutathione were also discussed. Hydrodynamic voltammogram was also recorded for the electrocatalytic oxidation of the sulfhydryl compounds. Amperometric determination and studies on the stability of the electrode for a period of 10 days were also carried out.