Enzyme-free electrochemical detection of nanomolar levels of the organophosphorus pesticide paraoxon-ethyl by using a poly(N-isopropyl acrylamide)-chitosan microgel decorated with palladium nanoparticles.

A rapid voltammetric method is described for the determination of the organophosphorus pesticide paraoxon-ethyl (PEL). A glassy carbon electrode (GCE) was modified with a composite consisting of a poly(N-isopropylacrylamide)-chitosan microgel with incorporated palladium nanoparticles. The microgel was characterized by FE-SEM, EDX, XPS, FTIR, XRD, and EIS. The modified GCE is shown to enable direct electro-reductive determination of PEL by using differential pulse voltammetry. The method works in pH 7 solution and in the 0.01 μM to 1.3 mM PEL concentration range. At a typical working potential of -0.66 V (vs. Ag/AgCl) (at 50 mV/s), the detection limit is as low as 0.7 nM, and the electrochemical sensitivity is 1.60 μA μM cm. Intriguingly, the modified GCE displays good recovery when applied to bok choy and water samples. Graphical abstract Schematic of an electrochemical method for determination of paraoxon ethyl (PEL) in bok choy extract and water by using poly(N-isopropyl acrylamide)-chitosan microgel decorated with palladium nanoparticle-modified glassy carbon electrodes (PdNPs/PNIPAM-CT microgel/GCE).