ABSTRACT Potentiometric electrodes based on the detection of choline esterase inhibition by analytes have been developed. The detection of choline esterase activity is based on the novel principle of molecular transduction. Immobilized peroxidase, acting as the molecular transducer, catalyzes the electroreduction of hydrogen peroxide by direct (mediatorless) electron transfer. The development of the following sensing elements are involved: screening different carbon-based electrode materials and modification of the electrode surface and testing of different types of enzyme immobilization. A number of different carbon-based materials were screened and tested: carbon fiber, felt and matt, graphite materials, and some highly dispersed carbon materials. A butyryl-choline sensitive, tri-enzyme electrode has been developed employing Teflonized carbon black as an electrode material of choice. The immobilization procedure is based on physical adsorption of peroxidase and co-immobilization of choline oxidase and choline esterase by the glutaraldehyde binding technique. Incubation of the electrode in a solution containing organophosphorus pesticide (trichlorfon) for 10 min results in a notable decrease of electrode activity. This allows for the determination of trichlorfon in nanomolar concentration with a detection limit of 1.3 ppb.
KEYWORDS: organophosphorus pesticide, determination, biosensor
This paper is from the Proceedings of the HSRC/WERC Joint Conference on the Environment, May 1996, published in hard copy and on the Web by the Great Plains/Rocky Mountain Hazardous Substance Research Center.
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