Development of Sol–Gel Immobilized Electrochemical Biosensor for the Monitoring of Organophosphorous Pesticides: A Voltammetric Method

Acetylcholinesterase (AChE) enzyme was immobilized through the silica sol–gel process onto the surface of carbon paste electrode (CPE). This fabricated monoenzyme biosensor on CPE was used as a working electrode. The enzyme biosensor on reaction with acetylthiocholine chloride (ASChCl or substrate), was found to be enzymatically hydrolyzed to thiocholine and acetic acid, which intern gave a disulfide compound and produced a larger anodic current at 0.63 V. The AChE biosensor was used for determining the two organophosphorous pesticides i.e. quinalphos and malathion in 0.1 M phosphate buffer/0.1 M KCl. The effect of scan rate, pH, enzyme loading and substrate concentration on the biosensor response was studied. Calibration graphs were performed for a concentration range of 20–300 ppb and 0.07–1.3 ppm for quinalphos and malathion respectively by employing the fabricated biosensor electrode. The limit of detection and limit of quantification values was found to be 8 ppb, 0.058 ppm and 26 ppb, 0.194 ppm for quinalphos and malathion respectively.