Development of an electroanalytical method using activated rice husk-derived carbon for the detection of a paraquat herbicide

Abstract

This work focused on the valorization of local lignocellulosic materials for analytical purpose. The electrode-modifying material was prepared by chemical activation of rice husks with phosphoric acid and calcined at 450 °C. The activated carbon obtained was characterized by different physicochemical and electrochemical techniques, namely yield and burn off during carbonization, apparent volumetric mass, Boehm titration, iodine number, Fourier transform infrared spectroscopy (FT-IR), CHN elemental analysis, pH at zero-charge point and Electrochemical Impedance Spectroscopy (EIS). These characterizations enabled us to have information on the functional groups present at the material surface, the mass percentage of the elements, the surface load of the material and the charge transfer resistance. The activated carbon thus obtained was used to develop a voltammetric sensor for the analysis of paraquat herbicide. Several parameters which assign the voltammograms to square wave voltammetry (SWV) were studied in order to optimize the developed sensor. The results obtained at optimal conditions are as follows: 10% of activated carbon in the carbon paste, electrolysis potential of −0.9 V, accumulation time of 8 minutes, pH of 8 and the pH at zero load point of 3.45. The results showed that the modified electrode is more sensitive and stable, thus can be used in electroanalysis of xenobiotics.