Graphite-Polyurethane Composite Electrode for the Electroanalytical Determination of Herbicide Diuron in Soil Solutions

This paper describes an electroanalytical procedure for the determination of the herbicide diuron in soil solutions using differential pulse voltammetry and a graphite-polyurethane electrode (GPU). Cyclic and differential pulse voltammograms showed an irreversible oxidation process at around +1.2 V (SCE), which was pH dependent and with the highest current peak at pH 1. The response of diuron on the GPU electrode was more defined and intense than for other carbon electrodes (glassy and carbon paste), probably due to a hydrophobic interaction between diuron and the GPU electrode material. The precision of the electroanalytical method, obtained from intraday and interday experiments, were 4.0% and 5.6%, respectively. Limits of detection and quantification were close to 10^–8 mol L^–1. The accuracy of the method, evaluated from recovering experiments in four soil solution samples fortified with diuron, varied from 94% to 99%, with the lowest values for the soil with the highest values of organic matter and clay content. Results showed that GPU is a very good material for the electroanalysis of diuron, and probably for other phenyl-urea-class pesticides, in complex media such as soil solutions.