CHEMILUMINESCENT FLOW SENSOR FOR THE DETERMINATION OF PARAOXON AND ALDICARB PESTICIDES

A chemiluminescence-based flow method for the determination of some organophorus and carbamate pesticides based on inhibition of acetylcholinesterase was developed. Acetylcholinesterase in solution or immobilized on methacrylate beads (Eupergit C) was coupled to choline oxidase and peroxidase immobilized on Eupergit C. In this system choline formed by acetylcholinesterase was oxidized by choline oxidase and the H2O2 produced was determined via the luminol/peroxidase luminescent reaction. The detection limits (3 sigma) for Paraoxon and Aldicarb were 0.75 mu g l(-1) and 4 mu g l(-1), respectively, when soluble acetylcholinesterase was used under the following optimized experimental conditions: 56 mu M luminol in working solution, sample volume 60 mu l, flow-rate 0.3 ml min(-1) and 60 min incubation time. The flow sensor device using all the three enzymes in the immobilized form had a higher detection limit of 125 mu g l(-1) for Paraoxon. The mid-range relative standard deviation (n = 10) using 1 mM standard substrate solution was 3.7%. The recovery from contaminated samples (soil, vegetables) varied from 81 to 108%. The results obtained by the developed methods were in good agreement with those obtained by a commonly used colorimetric test.