A glassy carbon electrode modified with a monolayer of zirconium(IV) phosphonate for sensing of methyl-parathion by square wave voltammetry.

A glassy carbon electrode (GCE) was consecutively modified with amino groups and phosphate groups, and then loaded with Zr(IV) ions. Fourier transform infrared spectrophotometry, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy and cyclic voltammetry were used to characterize the morphologies and electrochemical properties. The sensor was used to detect p-nitrophenyl-substituted organophosphorus pesticides, with methyl-parathion (MP) as the model analyte. Under optimized conditions, the oxidation current of square wave voltammetry (typically measured at around -0.28 V vs. saturated calomel electrode) increases linearly in the 1.0 to 100 ng mL-1 MP concentration range, and the detection limit is 0.25 ng mL-1 (at a signal to noise ratio of 3). Average recoveries from (spiked) real water samples are 99.9-102.2%, with relative standard deviations of 0.3-2.6% (n = 3) at three levels. The reliability and accuracy of the method was validated by HPLC. Graphical abstract Zr(IV) modified GCE is prepared via three steps. The electrode shows high specificity and selectivity towards methyl-parathion. And the linear range is 1.0 - 100.0 ng mL-1 with the detection limit as low as 0.25 ng mL-1 with SWV.