A highly sensitive and selective electrochemical sensor based on polythiourea modified glassy carbon electrode for detecting fenitrothion in vegetables

Abstract

A sensitive and selective sensor based on a polythiourea-modified glassy carbon electrode (polythiourea/GCE) was fabricated for electrochemical determination of fenitrothion (FT). Cyclic voltammetry and impedance spectroscopy were used to characterize the electrochemical behavior of polythiourea/GCE. The chemical and structural characteristics of the modified electrode were studied with UV-V is and FTIR spectroscopy techniques. The polythiourea (GCE) demonstrated faster electron transfer kinetics, a small charge transfer resistance, and an enhanced electroactive surface area of 0.173 cm2, which was two times greater than that of the bare GCE. The electrochemical behavior of FT at polythiourea/GCE was studied using cyclic voltammetry and square wave voltammetry. The reduction of FT on the surface of the modified electrode followed an adsorption-controlled process, and interestingly, the electrode surface coverage determined from chronocoulometric measurements showed 3.3 times higher accumulation of FT than at the bare GCE. Under optimized experimental parameters, the adsorptive stripping square-wave voltammetric current signal of FT at polythiourea/GCE exhibited an excellent sensitivity of 10.05 μA μM−1, good linearity ranging from 0.05 to 10 µM and 10–50 µM, and low limits of detection and quantification of 2.1 and 7.0 nM, respectively. The selectivity of the sensor was also evaluated in the presence of several common interfering substances, such as nitrophenol, malathion, diazinon, ascorbic acid, K+, Mg2+, and Zn2+ ions, and the percent error was less than ±5 %. The practical application of the suggested electrochemical sensor for FT determination was carried out in tomato, sweet potato, and cabbage samples. The average recoveries of the spiked samples were between 94.3 % and 110 %, indicating that the developed method is accurate for FT determination.