Enhancement of Amperometric Response to Tryptophan by Proton Relay Effect of Chitosan Adsorbed on Glassy Carbon Electrode

VERÓNICA I. PAZ ZANINI; RODRIGO E. GIMÉNEZ; OMAR E. LINAREZ PÉREZ; BEATRIZ A LÓPEZ DE MISHIMA; CLAUDIO D. BORSARELLI

ELSEVIER SCIENCE SA

Año: 2014

simply prepared, low-cost, and sensitive electrochemically activated glassy carbon electrode (GCEa) modified with absorbed chitosan (CHIT) film for quantification of tryptophan (Trp) is reported. Combination of cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques were used for characterization of the electro-oxidation of the amino acid and the electro-analytical performance of the CHIT-modified electrode. The electrooxidation of Trp involves an irreversible two-electron and two-proton transfer process in both bare and modified electrodes, but the adsorption of CHIT as a polycation onto GCEa produces a 4-fold increase of the oxidation current of Trp without changing both the oxidation potential and the heterogeneous reaction rate constant, suggesting that the biopolymer behaves as a proton relay species, probably due to hydrogen bonding/proton acceptor capability of hydroxyl and ether groups of CHIT. Finally,