Chitosan Nanocomposite Modified OPH-Based Amperometric Sensor for Organophosphorus Pesticides Determination

Background: The high acute toxicity of the organophosphorus pesticides (OPs) imposes the development of simple, rapid, sensitive, and reasonably priced analytical methods for their in situ determination. The electrochemical biosensors-based techniques for OPs determination complete with these requirements. Objective: The objective of this work was the development of an amperometric biosensor with improved analytical performances for the direct organophosphorus pesticides determination, applying a novel chitosan-based bionanocomposite for glassy carbon electrode (GCE) modification. Method: The bionanocomposite sensing platform was created by a simple, one-step electrodeposition onto the surface of the GCE of chitosan-entrapped carbon nanotubes (CS-CNTs), ZrO2 nanoparticles, and organophosphorus hydrolase (OPH). The electrochemical and analytical characterization of the modified electrodes was achieved by recording and analysing their CV, chronoamperometric, and amperometric responses. Results: The electroactive surface area of the CS-CNT-ZrO2-modified GCE (22.66 mm2), and its catalytic activity toward the electrochemical oxidation of p-nitrophenol, which is the product of the OPHcatalyzed hydrolysis of the nitrophenyl substituted OPs (catalytic rate constant 1.84 x103 L mol-1 s-1) were increased. The synergistic action of the CNTs and the ZrO2 nanoparticles also led to the improvement in the biosensor's analytical performances in comparison to the performances of the CS/OPH, CS-ZrO2/OPH, and CS-CNT/OPH modified GCEs; paraoxon was quantified with a sensitivity as high as 33.1 nA L μmol-1, dynamic concentration range extended up to 40 μmol L-1, and LOD as low as 20 nmol L-1. The determination was not affected by the presence of triazine pesticides and OPs without nitrophenyl substituents. The developed biosensor was applied for paraoxon determination in spiked samples of irrigation water with a satisfactory accuracy. Conclusion: An amperometric biosensor for OPs determination was developed using a novel bionanocomposite for GCE modification. The synergistic action of the individual components converted it in a high performant platform for the direct, sensitive, and selective paraoxon determination.