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 enzymemodified electrodes.The peak broadening was found to be determined by the geometry of the flow 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 enzymemodified electrodes at an applied potential of -0.05 V vs Ag/ AgCI.With the optimized cell low noise levels were obtained (<5 PA), allowing detection limits of 0.3, 6.0, and 20.0 pM for hydrogen peroxide, cumol hydroperoxide, and 2-butanone peroxide, respectively.Measurement in extremely small samplevolumes in various analytical exand in vivo methods requires sensitive, selective, and miniaturized detection devices.'V2Much work has been carried out on the development of enzyme-based microbiosensors, since they may meet the requirementse3-15 Several (1) Bindra, D.