Electrochemical characterization of repaglinide and its determination in human plasma using liquid chromatography with dual-channel coulometric detection

A simple, fast and sensitive HPLC method employing dual-channel coulometric detection for the determination of repaglinide in human plasma is presented. The assay involved extraction of repaglinide by ethyl acetate and isocratic reversed-phase liquid chromatography with dual-channel coulometric detection. The mobile phase composition was 50 mM disodium hydrogen phosphate/acetonitrile (60:40, v/v), pH of the mobile phase 7.5 set up with phosphoric acid. For all analyses, the first cell working potential was +380 mV, the second was +750 mV (vs. Pd/H2). Calibration curve was linear over the concentration range of 5–500 nmol L−1. Rosiglitazone was used as an internal standard. The limit of detection (LOD) was established at 2.8 nmol L−1, and the lower limit of quantification (LLOQ) at 8.5 nmol L−1. The developed method was applied to human plasma samples spiked with repaglinide at therapeutical concentrations. It was confirmed that the method is suitable for pharmacokinetic studies or therapeutic monitoring.