Analytica Chimica Acta, 284 (1993) 21-26 Elsevier Science Publishers B.V., Amsterdam 21 Amperometric glucose biosensor based on an electrocatalytically bulk-modified epoxy-graphite biocomposite F. Ckspedes, E. Martinez-Fhbregas and S. Alegret Grup de Sensors 81Biosensors, Lkpartament de Quhica, Vniverdat Aut&oma de Barcdonu, E-08193 Belkaterra,Catalonia (Spain) (Received 15th April 1993; revised manuscript received 16th July 1993) An inexpensive, robust, polishable and easily machinable amperometric glucose transducer was constructed. The biocomposite materials used were graphite, palladium-gold, nonconducting epoxy resin and glucose oxidase. The enzyme retains its bioactivity in the rigid epoxy-graphite matrix. The electrocatalytic oxidation of hydrogen peroxide is enhanced by gold-palladium and it is used as the analytical signal (at 900 mV vs. Ag/AgCl in a pH 7.00 buffered solution with 0.1 M phosphate and 0.1 M KCl). The biosensor exhibits a linear response to glucose in the 0.01-2 mM range and produces steady-state signals within a few seconds (6 s for 95% signal). Simple polishing procedures can be used to generate a fresh bioactive transducer surface. &ywo&s~ Amperometry; Biosensors; Catalytic methods; Biocomposites; Glucose biosensor; Epoxy-graphite biocom- Chemically or physically modified electrodes are very versatile and hold a great promise for electroanalytical applications [1,2]. This is the reason behind the significant research and devel- opment efforts seen recently in the field of am- perometric devices. The resulting electrodes are increasingly sensitive, selective, stable and inex- pensive. They are seen as a viable alternative to bulky and costly analytical equipment, especially in the control and monitoring of biomedical, envi- ronmental and industrial processes. In spite of all these advantages, modified amperometric devices have not been widely used as they have not been commercially available. The main reason for this disparity is that modified electrodes are difficult to prepare, especially when activating the surface Correspondenceto: S. Alegret, GNP de Sensors & Biosensors, Departament de Qufmica, Universitat Autonoma de Barcelona, E-08193 Bellaterra, Catalonia (Spain). of the electrode without loss of sensitivity, or when attaching modifiers to the electrode using covalent bonds, adsorption, polymer film coating, etc. Enzyme-based amperometric sensors are widely studied at present. Such devices can be seen as biologically modified electrodes. Several immobilization methods have been studied for the construction of electrochemical biosensors, depending on the specific biocatalyst. Generally, the biological component is immobilized on the surface of the electrode either by physical (using membranes) or chemical means (using covalent bonding or chemical cross-linking). Alternatively, the biocomponent can be incor- porated to the matrix of the transducer. An ex- ample of such bulk-phase modified electrodes is the popular carbon paste electrode. However, the nature of this paste is such that the resulting devices do not show sufficient chemical or me- tXlO3-2670/93/$06.00 0 1993 - Elsevier Science Publishers B.V. All rights reserved