Electrochemical Oxidation of Metolazone at a Glassy Carbon Electrode

Metolazone is a diuretic agent used in patients with edematous states and/or hypertension. The electrochemical behavior of metolazone on a glassy carbon electrode was investigated using cyclic, differential pulse, and square-wave voltammetry at different pHs. The pH dependent oxidation of metolazone occurs in two consecutive steps in a diffusion-controlled mechanism and involves the formation of a main oxidation product. The first oxidation process is reversible, and involves two electrons and two protons corresponding to the oxidation of nitrogen in the sulfonamide moiety. The second oxidation process is irreversible, also occurs in the sulfonamide moiety, involves a one electron-transfer, and is followed by deprotonation to produce a cation radical, which reacts with water and yields a hydroxylated product. The diffusion coefficient of metolazone was calculated to be 3.43 X 10(-6) cm(2) s(-1) in pH 7.0 0.1 M phosphate buffer.