Graphite-Polyurethane and Graphite-Silicone Rubber Composite Electrodes for Electrochemical Characterization and Determination of Minoxidil

Graphite‐polyurethane (GPUE) and graphite‐silicone rubber (GSRE) electrodes have been used for oxidative determination of the vasodilator minoxidil in pharmaceutical samples and in plasma and urine electrolyte solutions. The electrooxidation process at 0.840 V (GPUE) and 0.860 V (GSRE) vs. SCE was characterized over a wide pH range by cyclic voltammetry and electrochemical impedance spectroscopy. Quantification using cyclic, differential pulse, and square‐wave voltammetry, gave results agreeing with high pressure liquid chromatography, that has similar micromolar detection limits, but with a simpler analytical procedure. Advantages of these composite electrodes are non‐adsorption of analyte or oxidation products, a long useful life and robustness.