COLORIMETRIC DETECTION OF ORGANOPHOSPHATE PESTICIDES USING POLYDIACETYLENE VESICLES WITH ACETYLCHOLINESTERASE AND SURFACTANTS

Abstract

Organophosphate pesticides have been widely used in agriculture and in domestic purposes. It has posed serious concern for food and water contamination. Numerous of these pesticides, especially for dichlorvos, possess both acute and chronic toxicity posing hazardous risks to humans and environment. A new colorimetric method for the detection of dichlorvos based on polydiacethylene and acetylcholinesterase inhibition is developed. The blue-to-red color transition of poly(10,12-pentacosadynoic acid) vesicles can be induced by myristoylcholine which is enzymatically hydrolyzed by acetylcholinesterase to myristic acid and choline that prevents the color transition. In the presence of dichlorvos, the hydrolytic activity of the enzyme is inhibited that the blue-to-red color transition is restored with a linear correlation to the dichlorvos concentration with good selectivity over other organophosphate pesticides. Using UV-vis absorption spectrometer, the limit of detection is 6.7 ppb dichlorvos and the detection of 150 ppb by naked eye observation is possible. Sensitivity improvement of the naked eye detection to 50 ppb is achieved by mixing dimiristoylphosphatidylcholine to the diacetylene lipid in the preparation of the polydiacetylene vesicles. Development of paper-based poly(PCDA) indicator was attempted but it gave less sensitivity with the detection of 500 ppb for naked eye detection.