DETERMINATION OF ORGANOPHOSPHORUS AND CARBAMIC PESTICIDES WITH AN ACETYLCHOLINESTERASE AMPEROMETRIC BIOSENSOR USING 4-AMINOPHENYL ACETATE AS SUBSTRATE

Organophosphorus and carbamic pesticides have been determined with an amperometric acetylcholinesterase-based 4-aminophenyl acetate biosensor. The glassy carbon enzyme membrane covered electrode poised at +250 mV (vs. sodium chloride saturated calomel electrode) oxidizes the 4-aminophenol formed in the hydrolysis of 4-aminophenyl acetate by acetylcholinesterase in the glutaraldehyde cross-linked layer. The activity of acetylcholinesterase is inhibited in the presence of pesticides. The decrease in activity of the enzyme is monitored by the 4-aminophenyl acetate sensor and is correlated to the concentration of pesticide present in solution. The influence of the acetylcholinesterase loading and the acetylcholinesterase to neutral protein (bovine serum albumin) ratio on the biosensor response was studied and the measuring conditions including pH, substrate concentration, and others were optimized. Detection limits of 4.0 and 13.0 nmol l(-1) for paraoxon and carbaryl, respectively, were achieved with a 3-min preincubation time.