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Abstract
Simple portable potentiometric biosensor has been assessed for rapid in-field detection of neurotoxic anticholineesterase pesticides. The proposed biosensor based on inhibition of the acetylcholinesterase enzyme (AChE) by carbamate, organophosphorous pesticides, namely; methomyl, prothiofos and chlorpyrifos. Comprehensive studies were performed for the optimum measuring parameters for each pesticide and its degradation products. Based on the relative inhibition action of pesticide on AChE activity, different sensitivities were recorded ranging between 0.25 ng to 37.5 µg mL-1 depending on the nature of pesticide tested and its detoxification affect (LD). From different degradation products of methomyl, inhibition by methomyl S-oxide and methomyl S,S-dioxide were more potent allowing determination of 0.20 and 0.088 ng mL-1, respectively. Reasonable average recoveries ranging between 96.22±1.98 and 106.02±2.10 % were obtained. The applicability of the proposed method was tested by determination of pesticides in their commercial formulation and agricultural drainage water samples without pre-treatment procedures. Acceptable sensitivity and accuracy were obtained compared with the official chromatographic method indicated by good average recoveries between 94.73±2.74 and 108.3±0.80 %. The proposed sensors are promising and can be used as simple and direct screening devices for pesticide monitoring in field conditions available to unskilled end-users with significant decrease in cost per analysis to complement or replace the classical chromatographic methods.