DETERMINATION OF ORGANOPHOSPHORUS AND CARBAMATE PESTICIDE STANDARDS BY LIQUID-CHROMATOGRAPHY WITH DETECTION BY INHIBITION OF IMMOBILIZED ACETYLCHOLINESTERASE

A sensitive method for post-column reaction detection of carbamate and organophosphorus pesticides is described, based on the inhibition of immobilized acetylcholinesterase. The compounds are separated by reversed-phase liquid chromatography with tetrahydrofuran-water as the mobile phase in a isocratic system. The reactor used for detection comprises a conventional flow injection assembly for monitoring activity of acetylcholinesterase immobilized on controlled pore glass in a mini-column with spectrophotometric detection. The detection limits and linear calibration ranges are 2.6 and 5-40 ng for paraoxon, 0.04 and 0.1-1.6 ng for diisopropylfluorophosphate, 18 and 20-100 ng for isopropyl N-phenyl-carbamate and 29 and 40-400 ng for isopropyl N-(3-chlorophenyl)carbamate. Only 16 min is required for the determination of a mixture of the above pesticides, and each enzyme column can be used for 90 determinations.