DETERMINATION OF ANTICHOLINESTERASE PESTICIDES IN REAL SAMPLES USING A DISPOSABLE BIOSENSOR

A choline amperometric biosensor based on screen-printed electrodes wa s assembled and used to assess the inhibitory effect of organophosphor us and carbamic pesticides on acetylcholinesterase activity both in st andard solutions and real samples, Acetylcholinesterase catalyses the cleavage of acetylcholine to choline and acetate, therefore the amount of choline measured using the biosensor is directly related to the en zyme activity. The extent of enzyme inhibition can be used as an index of the amount of anticholinesterase pesticides present. The hydrophob icity of organophosphorus and carbamic pesticides led to the evaluatio n of organic, water miscible solvents for use in the proposed method. Berate buffer containing 1% v/v acetonitrile was selected since it exh ibited the least influence on enzyme activity from the tested solvents (acetonitrile, acetone, tetrahydrofuran and ethylacetate). Other solv ents (dimethylsulfoxide and methanol) were avoided as they exhibited e lectrochemical interferences. An inhibition calibration curve was obta ined using carbofuran, a strong inhibitor of acetylcholinesterase. The lowest detectable standard solution (mean +/-3 standard deviation of the blank) was 2 mu gl(-1) following an incubation time of 10 min. The method was then applied to real samples (fruits and vegetables) showi ng its suitability as a rapid screening assay (12 min per test) for th e assessment of anticholinesterase pesticides, The biosensor results w ere compared with a standard analytical technique (gas chromatography with nitrogen phosphorus detector, GC-NPD).