Reactivation of an immobilized enzyme reactor for the determination of acetylcholinesterase inhibitors Flow injection determination of paraoxon

Abstract A stopped-flow/flow-injection procedure is proposed for the spectrophotometric determination of paraoxon based on the inhibition of immobilized acetylcholinesterase. The irreversibly inhibited enzyme is reactivated with 1,1′-trimethylene-bis(4-formylpyridinium bromide) dioxime. The proposed procedure has a detection limit of 4 × 10−9 M, a linear calibration range of 9 × 10−9−5 × 10−7 M, a R.S.D. of 1.6% (n = 10) at 5.0 × 10−8 M and a sample throughput frequency of 10 h−1. The enzyme reactor can be used for more than one thousand inhibition-reactivation cycles.