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
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
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.