Validation of the assay of metoprolol in human plasma using liquid-liquid extraction and high performance liquid chromatography with fluorescence detection

Metoprolol was successfully assayed in human plasma samples. The sample preparation procedure was based upon liquid-liquid extraction, using propranolol as internal standard (I.S.). The HPLC procedure developed using a Merck Chromolith column was based on the ion pairing separation mechanism. Fluorescence detection (ex. 230 nm; em. 305 nm) provided an excellent delectability (the determined quantitation limit, LOQ was 7.5 ng mL(-1)). Both sample preparation and chromatographic procedure were validated and used in a single-dose comparative bioequivalence study carried out on thirteen healthy volunteers. The same column was used for the entire determination and no major alteration of the separation behaviour was observed.