APPLICATIONS OF WIRED PEROXIDASE ELECTRODES FOR PEROXIDE DETERMINATION IN LIQUID-CHROMATOGRAPHY COUPLED TO OXIDASE IMMOBILIZED ENZYME REACTORS

An osmium poly(vinylpyridine) redox polymer ''wired'' horseradish pero xidase electrode has been used to detect H2O2 for the determination of glucose, lactate, and acetylcholine/choline with liquid chromatograph y (LC) and postcolumn immobilized enzyme reactors (IMERs). The redox p olymer film containing peroxidase is coated on the surface of a glassy carbon electrode and operated at +100 mV vs Ag/AgCl for the reduction of H2O2. Compared with a conventional platinum electrode oxidizing H2 O2 at +500 mV vs Ag/AgCl, the peroxidase cathode exhibits a 2-10-fold improvement in sensitivity and detection limit. The enzyme electrode a lso shows better operational stability than the Pt electrode. When the enzyme electrode is coupled to LC oxidase IMER systems, the initial s tabilization of the background current is significantly faster than th at for the conventional Pt electrode. The enzyme electrode has been us ed to determine glucose and lactate concentrations in rat subcutaneous microdialysates. After 8 days of continuous injection of the dialysat e samples, the enzyme electrode sensitivity dropped by only 5%.