A Simple Colorimetric Enzymatic-Assay, based on immobilization of acetylcholinesterase by adsorption, for sensitive detection of organophosphorus insecticides in olive oil

Over the last decades, cholinesterase (ChE) biosensors/bioassays have emerged as an ultra sensitive and rapid technique for pesticides detection in environmental monitoring, food and quality control. In this work a Simple Colorimetric Enzymatic-Assay for the sensitive detection of three organophosphorus insecticides widely used in the treatment of olive trees: Malathion, Dimethoate and Methidathion in their oxidized form was developed. The systems are based on the immobilization of 0.3 mIU of electric eel acetylcholinesterase by adsorption on MaxiSorp™ microplates, and tested using standard solutions and real samples of olive oil. The developed colorimetric tests showed good analytical performances with limits of detection as low as 10−9 M for the widely used pesticide malaoxon (oxidized malathion), as well as a good reproducibility, good operational and storage stability and they can be applied directly on olive oil real samples without a laborious pre-treatment and after a simple liquid–liquid extraction, which demonstrate the potentiality of this technique to be used for commercial purpose.