Electrochemical Detector for Liquid Chromatography: Determining Minoxidil in Hair-Growth Pharmaceuticals

Background: The electrochemical behavior of minoxidil on gold (Au), Glassy Carbon (GCEs), and Carbon Paste Electrodes (CPEs) was investigated in an aqueous supporting electrolyte (phosphate buffer [pH 2.0-6.5], acetate buffer [pH 4.3], and Britton and Robinson buffer [pH 2.0-7.4]). Methods: For cyclic voltammetric measurements with suitable methodical parameters, CPEs catalyze electrooxidation of minoxidil more efficiently than do other electrodes. Minoxidil was detected using high-performance liquid chromatography with an electrochemical (carbon paste) detector (HPLCECD). For direct current mode, with the current at a constant potential, and measurements with suitable experimental parameters, a linear concentration from 0.02 to 2.6 mg L-1 was found. The detection limit was approximately 20 ng m L-1. Results: The developed method detected minoxidil samples. Conclusion: Findings using HPLC-ECD and HPLC with an ultraviolet detector were comparable.