AMPEROMETRIC PEROXIDE SENSOR-BASED ON HORSERADISH-PEROXIDASE AND TOLUIDINE BLUE O-ACRYLAMIDE POLYMER IN CARBON-PASTE

An amperometric enzyme electrode for monitoring hydrogen peroxide (H2O 2) was constructed by coimmobilising periodate oxidised horseradish pe roxidase (HRP) and a redox polymer containing a covalently bound pheno thiazine type mediator, toluidine blue O (TBO), in a carbon paste matr ix. Two different carbon paste electrodes were designed using either p araffin oil or solid paraffin wax as binders. A new mode of preparing enzyme modified carbon-wax composites is presented based on dissolving the wax in n-pentane before mixing with the enzyme modified carbon po wder excluding the necessity of melting the wax prior to mixing. The d eveloped sensors were used in a flow-injection system at an applied po tential of -50 mV vs. Ag/AgCl. Both electrode configurations displayed superior storage and operational stability, compared with similarly p repared electrodes containing only native HRP, where the electrical co mmunication was based on a direct electron transfer between the electr ode and HRP. Detection limits (calculated as twice the signal to noise ratio) of 50 nM H2O2 were obtained for these electrodes. (C) 1998 Els evier Science B.V. All rights reserved.