Spectrophotometric determination of organophosphoric insecticides in a FIA system based on AChE inhibition

This work presents a FIA system for pesticide analysis in water based on irreversible inhibition of acetylcholine esterase by organophosphoric insecticides with spectrometric determination of thiocholine with Ellman's reagent. The enzyme was immobilized on amminated glass pearls kept into a reactor and reactivated with 2-PAM after each inhibition step. The total toxic substances of real sample is expressed as equivalent paraoxon and calculated based on relative inhibition of the enzyme measuring the FIA peaks high before and after inhibition. The calibration graph was linear between 2 and 70 ppb paraoxon at an incubation time of 20 min. The LOD was 1.3 mug/L. A complete analysis lasted 35 min. The method was used for analysis of real water samples.