Voltammetric study of the extractant 4-methyl-N-quinolin-8-ylbenzenesulfonamide at a carbon paste electrode

Abstract

An electroanalytical study of 4-methyl-N-quinolin-8-ylbenzenesulfonamide, a model compound of similar structure to that of the active component in the commercial extractant LIX 34, at a carbon paste electrode, has been carried out using different voltammetric techniques. The compound was oxidized in methanolic medium (methanol– H₂O, 20 + 80), with Britton–Robinson buffers as supporting electrolytes and KCl solution (ionic strength 1 mol l^–1), giving rise to a voltammetric peak in the pH range 1.2–12.0. The effect of pH on the anodic voltammograms has been studied and the graph of E_pversus pH shows two straight lines intercepting at a pH value of 9.6. The oxidation process for the compound is irreversible (αn= 0.63) and predominantly diffusion controlled, although with an important adsorptive component. The electrode process can be attributed to the oxidation of the sulfonamide group. A voltammetric method for the determination of the compound has been developed and has been applied to samples of LIX 34.