Electrocatalytic oxidation and nanomolar determination of guanine at the surface of a molybdenum (VI) complex-TiO2 nanoparticle modified carbon paste electrode

A modified carbon paste electrode was prepared by incorporating TiO2 nanoparticles with bis[bis(salicylidene-1,4-phenylenediamine)molybdenum(VI)]. A mixture of fine graphite powder with 4 wt% of TiO2 nanoparticles was applied for the preparation of the carbon paste (by dispersing in paraffin) and finally modified with a molybdenum (VI) complex. The electrocatalytic oxidation of guanine (G) was investigated on the surface of the molybdenum (VI) complex-TiO2 nanoparticle modified carbon paste electrode (MCTNMCPE) using cyclic voltammetry (CV), differential pulse voltammetry (DPV), chronoamperometry (CHA) and chronocoloumetry (CHC). Using the modified electrode, the kinetics of G electrooxidation were considerably enhanced by lowering the anodic overpotential through a catalytic fashion. The mechanism of G electrochemical behavior at the modified electrode surface was analyzed by various electrochemical methods. The prepared modified electrode showed voltammetric responses with high sensitivity for G, making it very suitable for the detection of G at nanomolar levels. A linear dynamic range of 7.0-200 nM for G was obtained in buffered solutions with pH 5.0. The detection limit was 3.4 nM. (C) 2008 Elsevier B.V. All rights reserved.