PEROXIDASE-MODIFIED CARBON-FIBER MICROELECTRODES IN FLOW-THROUGH DETECTION OF HYDROGEN-PEROXIDE AND ORGANIC PEROXIDES

Mediatorless amperometric microbiosensors, prepared by immobilizing two different peroxidases [horseradish peroxidase (HRP) or peroxidase from Arthromyces ramosus (ARP)] on high-modulus-type carbon fibers, were applied for detection in flowing solution. The preparation and performance of the enzyme-modified carbon fibers were studied. An electrochemical flow-through cell containing the fiber electrode was evaluated and optimized. The influence of the electrode dimensions and the flow rate on the sensitivity and the sample dispersion in the cell was studied by use of bare and enzyme-modified electrodes. The peak broadening was found to be determined by the geometry of the now cell. The response time of the enzyme-modified electrode was short (<4 s) and did not contribute significantly to the peak broadening. When operated in a flow injection (FI) system, hydrogen peroxide and organic peroxides could be detected with the enzyme-modified electrodes at an applied potential of -0.05 V vs Ag/AgCl. With the optimized cell low noise levels were obtained (<5 pA), allowing detection limits of 0.3, 6.0, and 20.0 mu M for hydrogen peroxide, cumol hydroperoxide, and 2-butanone peroxide, respectively.