Determination of hydrogen peroxide using glassy carbon and graphite/polyester composite electrodes modified by vanadium-doped zirconias

Synthetic monoclinic and tetragonal vanadium-doped zirconias (VZrO2) with vanadium loading ranging from 0.5 to 15 mol% are used to modify glassy carbon and graphite/polyester composite electrodes able to detect oxygen and hydrogen peroxide in neutral aqueous media. Electrodes modified by monoclinic VZrO2 decrease the overpotential for the reduction of oxygen and hydrogen peroxide in neutral and alkaline media and enhance their reduction currents with respect to unmodified carbon electrodes. This is associated to seven-coordinated vanadium centers isomorphously substituting zirconium ones in the ZrO2 lattice. The catalytic effect shows site-selectivity, since it is almost entirely absent in tetragonal VZrO2 in which eight-coordinated vanadium sites exists. Under optimized conditions using differential pulse detection mode, the height of the cathodic catalytic current peak is directly proportional to the hydrogen peroxide concentration over the concentration range 5-400 muM with a sensitivity of 170 muA/mM at pH 10.0. The detection limit (3sigma) is calculated as 0.9 muM. (C) 2002 Elsevier Science B.V. All rights reserved.