ENZYME SENSORS FOR THE DETECTION OF PESTICIDES

Various families of pesticides (insecticides, fungicides and herbicides) can be detected using enzymes. Organophosphorus and carbamate insecticides (e.g. paraoxon, methyl-parathion, aldicarb and carbofuran) inhibit acetylcholinesterase; dithiocarbamate fungicide (e.g. maneb) inhibits aldehyde dehydrogenase; and sulfonylurea herbicides (e.g. sulfomethuron methyl and thifensulfuron methyl) inhibit acetolactate synthase. When these pesticides are in the presence of these enzymes, their activity decreases. We have monitored this decrease with a thiocholine sensor for acetylcholinesterase, a NADH sensor for aldehyde dehydrogenase and spectrophotometrically for acetolactate synthase. In all cases detection is better than those obtained by CPG (gas phase chromatography), colorimetric or HPLC (high performance liquid chromatography) methods. We can detect 0.02 ppb equivalent paraoxon, 0.05 ppm maneb and 19 ppb thifensulfuronmethyl.