Anal Bioanal Chem (2006) 386: 1413–1418 DOI 10.1007/s00216-006-0682-0 ORIGINAL PAPER T. Dodevska . E. Horozova . N. Dimcheva Electrocatalytic reduction of hydrogen peroxide on modified graphite electrodes: application to the development of glucose biosensors Received: 3 May 2006 / Revised: 30 June 2006 / Accepted: 14 July 2006 / Published online: 12 September 2006 # Springer-Verlag 2006 Abstract The electrocatalytic activities of a series of compact graphites modified with microquantities of plat- inum metals (Pd or Pt+Pd) towards the electrochemical reduction of hydrogen peroxide were characterised. Operational parameters such as the optimal working potential, the influence of temperature and the resulting electrode characteristics were examined. The benefits of using graphite modified with Pt+Pd (mixture ratio 30%:70%) as the basic transducer in a glucose biosensor with improved sensitivity were demonstrated. It was proven that, under the working conditions chosen, the selected electrode (whether bare or covered with an enzyme layer) did not respond to any glutathione, uric acid or ascorbic acid (which all normally occur in biological fluids) present. Keywords Modified graphite electrodes . Hydrogen peroxide . Electroreduction . Glucose biosensor Introduction Hydrogen peroxide is utilized in a wide range of industrial applications: from food processing (e.g. in the cold pasteurisation of milk, wine ageing, etc.) and textile bleaching to cosmetics and pharmaceutical manufacturing. While assays of relatively large H 2 O 2 concentrations can be performed using either classical redox titration or optical methods such as spectrophotometrical determination [1], electrochemical methods and (in particular) amperometric techniques show many advantages for the detection of submilimolar levels of peroxide, such as low detection limits and an extended linear range of the electrode response as a function of the peroxide concentration. Indeed, there is great demand for simple and efficient electrochemical peroxide monitoring techniques, not only from industry, but also from those involved in biosensor development. Because of their ability to oxidize peroxide at a low overpotential, platinum electrodes were the first to be applied to enzyme electrodes for blood glucose evaluation [2, 3]. Their high operational stability have made them exceptional performers in the glucometric devices that have been made commercially available so far. The main drawback of electrooxidation-based sensors is, however, that a variety of substances normally present in biological samples (uric and ascorbic acids, glutathione, neurotrans- mitters, drugs) oxidized at potentials below the working potential can contribute to the response output, thus resulting in overestimated analyte levels. Most research efforts aimed at overcoming this problem have focused on the development of electrocatalytic systems based on H 2 O 2 electroreduction. Horseradish [4–7] and other plant peroxidases [7–9], immobilized on mostly carbonaceous transducers, as well as some heme proteins [9–12], have attracted much interest since they are efficient catalysts of the electrochemical reduction of hydrogen peroxide at working potentials around zero mV (vs. SCE, in neutral solutions), which ensures interference-free responses. Despite the high selectivity and sensitivity of these biosensors, the fragile operational stability of biologically derived material makes them more suitable for the construction of single- rather than repeated-use sensing elements. Modification of the electrode surface with iron hexa- cyanoferrate (Prussian blue: also known as artificial peroxidase [13]) offers an electrode material that electro- T. Dodevska Department of Inorganic and Physical Chemistry, University of Food Technology, 26, Maritsa blvd., Plovdiv 4002, Bulgaria E. Horozova (*) . N. Dimcheva (*) Department of Physical Chemistry, Plovdiv University, 24, Tsar Assen st., Plovdiv 4000, Bulgaria e-mail: horozova@argon.acad.bg e-mail: ninadd@argon.acad.bg