DETERMINATION OF ORGANOPHOSPHORUS INSECTICIDES WITH A CHOLINE ELECTROCHEMICAL BIOSENSOR

Organophosphorus insecticides have been determined with an amperometric hydrogen peroxide based choline biosensor. This class of pesticides inhibits cholinesterase enzymes which in the presence of their substrates produce choline. The decrease in activity of these enzymes is monitored by the choline sensor and is correlated to the concentration of pesticide present in solution. Pesticides such as paraoxon, parathion, methyl paraoxon and methyl parathion have been coupled with acetylcholine and butyrylcholine esterases. Results showed that although the enzyme activity of acetylcholinesterase (AChE) was higher than butyrylcholinesterase (BuChE), the lower specificity of BuChE resulted in a higher enzyme inhibition. The detection limit was less than 1 ppb with an incubation time of 120 min and 2 ppb when the incubation time was 30 min. This method has been applied to the analysis of pesticides in water samples. Results, compared with those obtained with a different analytical procedure (liquid/liquid extraction and GLC determination), demonstrated that our method is a good analytical choice to measure the total anticholinesterase activity in water samples.