Pulsed electrochemical detection of H2O2 on gold

The voltammetric oxidation of hydrogen peroxide at a polycrystalline gold electrode, in neutral and alkaline media, shows two oxidation waves. At pH 7.4, one wave occurs at +490 mV and the second one at +870 mV vs Ag/AgCl. The latter appears at the expense of the first one. Formation of the first wave is favoured by the presence of an adsorbed layer of hydroxyl-groups on gold but its magnitude is markedly affected by adsorbed interfering species and gold oxide structures. The quantitative analysis of hydrogen peroxide, using the first wave, is possible by preferably applying a pulsed electrochemical cleaning with a detection at +550 mV. In flow injection analysis the response of hydrogen peroxide is linear over a wide concentration range i.e., 7 mu M-0.1 M with a detection limit of 3 mu M. The inhibition of H2O2 oxidation by an interfering species is suitable for the indirect quantitative analysis of species which are readily adsorbed on gold. This is shown in flow injection analysis by recording a stable oxidation current due to hydrogen peroxide in the carrier stream with detection of the inhibition of the signal due to the adsorbed species. Application to a surfactant such as Triton X100 at concentrations as low as 0.3 mu M is reported. (C) 1998 Elsevier Science Ltd. All rights reserved.