Electrochemical Behavior of Verapamil at Graphite–Polyurethane Composite Electrodes: Determination of Release Profiles in Pharmaceutical Samples

Abstract

A solid graphite–polyurethane composite electrode has been used to determine release profiles of verapamil, a calcium-channel blocker. The electro-oxidation process was characterized by cyclic voltammetry and electrochemical impedance spectroscopy and showed no adsorption of analyte or oxidation products, unlike at other carbon-based electrodes. Quantification gave linear ranges up to 40 µmol L⁻¹ with cyclic voltammetry and detection limits of 0.7 µmol L⁻¹ by differential pulse and square-wave voltammetry. Commercial product samples were successfully analyzed with results equal to those from spectrophotometry. Because no electrode surface renewal is needed, this electrode material has many advantages.

Keywords:

• Composite electrode
• release profile
• verapamil

Acknowledgments

Financial support from the Brazil/Portugal bilateral agreement (CAPES/FCT 177/07) and CEMUC (Research Unit 285), Portugal (FCT), is gratefully acknowledged. F. S. S. thanks CAPES for a postdoctoral grant (3183/07-6).