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 biosenso r. The glassy carbon enzyme membrane covered electrode poised at +250 mV (vs. sodium chloride saturated calomel electrode) oxidizes the 4-am inophenol formed in the hydrolysis of 4-aminophenyl acetate by acetylc holinesterase in the glutaraldehyde cross-linked layer. The activity o f 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 pre sent in solution. The influence of the acetylcholinesterase loading an d the acetylcholinesterase to neutral protein (bovine serum albumin) r atio on the biosensor response was studied and the measuring condition s including pH, substrate concentration, and others were optimized. De tection limits of 4.0 and 13.0 nmol l(-1) for paraoxon and carbaryl, r espectively, were achieved with a 3-min preincubation time.