Determination of metoprolol enantiomers in human urine by coupled achiral-chiral chromatography

Achiral-chiral column switching HPLC assay was developed to allow the separ ation and quantitation of the enantiomers of metoprolol in human urine by m eans of fluorescence detection. Urine samples were prepared by liquid-liqui d extraction, followed by HPLC. The racemic metoprolol and internal standar d were separated from the interfering components in urine and quantified on the silica column, and the enantiomers were determined on a Chiralcel OD c hiral stationary phase. The two columns were connected by a switching valve equipped with a silica trap column. Detection limit was 25 ng/ml for each enantiomer. The intra-day variation ranged between 0.38 and 4.94% in relati on to the measured concentration and the inter-day Variation was 0.15-3.13% . It has been applied to the determination of (R)-(+)-metoprolol and (S)-(- )-metoprolol in urine from healthy volunteers dosed with racemic metoprolol tartrate. (C) 2000 Elsevier Science B.V. All rights reserved.