Modified glassy carbon electrodes obtained by electrochemical treatment. Effects on the heterogeneous electron transfer kinetics of an adsorbed aromatic amine

Glassy carbon (GC) electrodes were modified by polishing and electrochemical pre-treatment (ECP) in an acidic aqueous medium to obtain a reproducible kinetic response. The surface state was characterised by an electrochemical parameter, eo, which has been demonstrated to be proportional to the number of surface sites susceptible of oxidation. A probe molecule N,N,N',N'-tetramethyl- 1,1'-naphthidine (TMN) was adsorbed on the modified GC by interacting with specific chemical sites. The amount of adsorbed TMN measured by cyclic (CV) and linear sweep voltammetry (LSV) varies linearly with eo. By using this relation, it is possible to predict the degree of surface modification. An EE oxidation mechanism was proposed for the adsorbed probe molecule and the kinetic constants were calculated by a semiempirical method using experimental data and the resolution of differential equations by use of Simnon(TM) software. In addition, ECP does not change the electronic sites that promote the electron transfer and the observed transfer rate constant is riot affected by different degrees of electrochemical modification (measured through Q(0) values). Thus, the procedure gives a reproducible modified GC\aqueous electrolyte interface for the electro-oxidation of the probe molecule. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.