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 peroxidase electrode has been used to detect H2O2 for the determination of glucose, lactate, and acetylcholine/choline with liquid chromatography (LC) and postcolumn immobilized enzyme reactors (IMERs). The redox polymer 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 H2O2 at +500 mV vs Ag/AgCl, the peroxidase cathode exhibits a 2-10-fold improvement in sensitivity and detection limit. The enzyme electrode also shows better operational stability than the Pt electrode. When the enzyme electrode is coupled to LC oxidase IMER systems, the initial stabilization of the background current is significantly faster than that for the conventional Pt electrode. The enzyme electrode has been used to determine glucose and lactate concentrations in rat subcutaneous microdialysates. After 8 days of continuous injection of the dialysate samples, the enzyme electrode sensitivity dropped by only 5%.