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

Mediatorless amperometric microbiosensors, prepared by immobilizing tw o different peroxidases [horseradish peroxidase (HRP) or peroxidase fr om Arthromyces ramosus (ARP)] on high-modulus-type carbon fibers, were applied for detection in flowing solution. The preparation and perfor mance of the enzyme-modified carbon fibers were studied. An electroche mical flow-through cell containing the fiber electrode was evaluated a nd optimized. The influence of the electrode dimensions and the flow r ate on the sensitivity and the sample dispersion in the cell was studi ed by use of bare and enzyme-modified electrodes. The peak broadening was found to be determined by the geometry of the now cell. The respon se time of the enzyme-modified electrode was short (<4 s) and did not contribute significantly to the peak broadening. When operated in a fl ow injection (FI) system, hydrogen peroxide and organic peroxides coul d be detected with the enzyme-modified electrodes at an applied potent ial of -0.05 V vs Ag/AgCl. With the optimized cell low noise levels we re obtained (<5 pA), allowing detection limits of 0.3, 6.0, and 20.0 m u M for hydrogen peroxide, cumol hydroperoxide, and 2-butanone peroxid e, respectively.