Detection of Anticholinesterase Agents in Drinking Water by use of Tandem Packed Bed Reactors with Human Red Blood Cell Acetylcholinesterase and Choline Oxidase in a Switching Flow System

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Abstract
A flow system for the sensitive monitoring of acetylcholinesterase (ACHE) inhibitors is reported. The mobile phase contained acetylcholine (ACH) and choline (CH) as substrates. Red blood cell membrane ACHE was adsorbed on glass fibres. A tandem packed bed bioreactor system with reactors containing ACHE and choline oxidase (CHO), respectively, converted acetylcholine and choline selectively to hydrogen peroxide which was continuously detected by an electrochemical detector. The presence of ACHE inhibitors caused decreases in ACHE activity and hydrogen peroxide production, the decrease of the response being proportional with the concentration, reaction time and inhibiting strength of the solutes. Switching of the reactors enabled the detection of substances which inhibit CHO (e.g. the oxime HLö 7, which is used for the regeneration of ACHE), stopped-flow injection of inhibitors and their long time reaction with ACHE. Flow kinetic studies of both CHO and ACHE were performed to determine optimum conditions for the measurement. The limits of detection for paraoxon and physostigmine in drinking water were found to be 1 nM, and for malathion and parathion-methyl, 2 μM and 8 μ, respectively.

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