Bi-enzyme Electrochemical Sensor for Selective Determination of Organophosphorus Pesticides with Phenolic Leaving Groups

An amperometric bi-enzyme sensor for detection of organophosphorus pesticides (OPs) with phenolic leaving groups, which are not electroactive, is presented in this work. The biosensing platform was created by a simple, controllable, and reproducible one-step electrodeposition onto the surface of a glassy carbon electrode of a chitosan bionanocomposite with entrapped carboxylated multi walled carbon nanotubes, organophosphorus hydrolase (OPH), and horseradish peroxidase (HRP). The OPs determination involved a sequence of OPH and HRP-catalyzed reactions resulting in phenolic radicals production, which were quantified by registering the current of their reduction at a potential of -50 mV vs. Ag, AgCl/KCl(sat.)The developed sensor was applied for the determination of prothiofos, as an example. At optimized conditions (pH 7.25 and H2O2 concentration 200 mu mol L-1), a LOD as low as 0.8 mu mol L-1 was attained, while the linear concentration range was extended from 2.64 molL(-1) up to 35 mu mol L-1. The main advantage of the proposed bi-enzyme sensor is its selectivity toward the OPs with phenolic leaving groups, excluding the interference of the nitrophenyl-substituted OPs.