Amperometric flow-through biosensor for the determination of cholinesterase inhibitors

An amperometric flow-through biosensor based on epoxy-carbon electrode and butyrylcholinesterase immobilised on nylon, cellulose nitrate or white tracing paper has been developed and examined for the determination of reversible and irreversible inhibitors. The analytical characteristics of inhibitor determination depend on the hydrophobicity of the membrane material. Flow-through biosensor with various enzymatic membranes makes it possible to determine fluoride in the concentration range 1 x 10(-4)-25 x 10(-4) mol l(-1) and 3.5 x 10(-5)-1 x 10(-2) mol l(-1) when cholinesterase solution is used. The analytical characteristics of fluoride determination do not differ significantly from those obtained in batch conditions. For diazinon the immobilisation of cholinesterase results in the decrease of detection limits from 5 x 10(-9) mol l(-1) (native enzyme) to 4 x 10(-9) mol l(-1) (nylon membrane) and 1.5 x 10(-9) mol l(-1) (cellulose nitrate membrane). The influence of membrane material on analytical characteristics of FIA determination of inhibitors is due to the non-stationary distribution of reagents (fluoride) or sorptional preconcentration of the inhibitor (diazinon) in membrane. (C) 1999 Elsevier Science B.V. All rights reserved.