Abstract: The electrocatalytic oxidation of NADH, ascorbate, urate, xanthine and H-2O-2 at different polypyrrole electrodes has been investigated. The conducting polymer was grown on platinum, glassy carbon, or graphite electrodes and modified by means of enclosed redox-active anions or other redox-active compounds covalently bound to either the N- or the β-position of the pyrrole. Copolymers of pyrrole and N-substituted pyrrole derivatives of chloranil or 2,3-dichloro-1,4-naphthoquinone showed outstanding electrocatalytic properties of the oxidation of NADH. The application of these electrodes in amperometric steady-state measurements or flow injection systems in combination with dehydrogenase reactions has been possible.

Abstract: A great number of enzyme-catalyzed reactions are accompanied by heat evolutions.1 Therefore, flow-injection analysis (FIA) based on calorimetry, that is, flow-injection calorimetry,2,3 in combination with biocatalysts as specific recognition elements gives convenient and versatile analytical methods for biorelated compounds. Nakatani and Shimizu purified a thermostable laccase from Trametes sp. and reported its enzymatic properties recently.4 The enzyme functioned as the catalyst in oxidative reactions of various kinds of dihydroxylated compounds (so-called polyphenol compounds). We tried to apply its enzymatic properties to the determination of L-ascorbate in soft drinks. In this paper, we describe the fundamental performance of the calorimetric FIA system with use of the enzymes immobilized onto porous glass beads.