Catalytic reduction of hydrogen peroxide at metal hexacyanoferrate composite electrodes and applications in enzymatic analysis

The electrocatalytic activity of various metal hexacyanoferrates (Mhcfs) (i) immobilized on graphite electrodes, and (ii) as components of a composite electrode was investigated with respect to the reduction of hydrogen peroxide. The flow-through working electrode was a thin layer consisting of a composite of Mhcf, graphite, and polymethylmetacrylate (PMMA) as a binder, sandwiched between two Plexiglas plates. Among the pure Mhcfs immobilized on a graphite electrode, iron(III) hexacyanoferrate (Prussian blue) exhibits the highest electrocatalytic effect, whereas in the composite electrodes chromium(III) hexacyanoferrate (Crhcf) shows the highest activity and best performance and reproducibility for the electrochemical reduction of H2O2. The Crhqf electrode provides a linear dependence on H2O2 concentration in the range 2.5 x 10(-6) mol L-1 (LOD) to 1 x 10(-4) mol L-1 (phosphate buffer, pH 7). The sensor was applied for the detection of H2O2 enzymatically produced by glucose oxidase. The optimal conditions for the peroxide injection were 2 min after the beginning of the reaction and 25 degrees C with a detection limit of 7.0 x 10(-6) mol L-1 for glucose. (c) 2006 Elsevier Ltd. All rights reserved.