Electrocatalytic oxidation of some amino acids on a nickel–curcumin complex modified glassy carbon electrode

This study investigated the electrocatalytic oxidation of alanine, l-arginine, l-phenylalanine, l-lysine and glycine on poly-Ni(II)–curcumin film (curcumin: 1,7-bis [4-hydroxy-3-methoxy phenyl]-1,6-heptadiene-3,5-dione) electrodeposited on a glassy carbon electrode in alkaline solution. The process of oxidation and its kinetics were established by using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy techniques. Voltammetric studies indicated that in the presence of amino acids the anodic peak current of low valence nickel species increased, followed by a decrease in the corresponding cathodic current. This indicates that amino acids were oxidized on the redox mediator which was immobilized on the electrode surface via an electrocatalytic mechanism. Using Laviron's equation, the values of α and ks for the immobilized redox species were determined as 0.43 ± 0.03 and 2.47 ± 0.02 × 106 s−1, respectively. The rate constant, the electron transfer coefficient and the diffusion coefficients involved in the electrocatalytic oxidation of amino acids were determined.