Identification and determination of the enantiomers of moprolol and their metabolites in human urine by high-performance liquid chromatography and gas chromatography-mass spectrometry.

A simple and sensitive high-performance liquid chromatographic (HPLC) method using chiral derivatization was developed to screen and determine the enantiomers of moprolol and their metabolites in human urine. The recovery of (+)- and (-)-moprolol from urine was 70.8-81.1% at different concentrations. The coefficients of variation (C.V.) were less than 3.2 and 6.5% for intra- and inter-assays, respectively. Moprolol could be detected in urine up to 24 h after oral administration of a 50-mg dose of moprolol. Unconjugated and conjugated enantiomers of moprolol and their metabolites were analyzed by gas chromatography (GC). A gas chromatographic-mass spectrometric (GC-MS) confirmatory method was established to identify the metabolites of moprolol. The double derivation procedure for moprolol and their metabolites with S-(-)-methyl chloroformate [(-)-MCF] and N-methyl(trimethylsilyl)trifluoroacetamide (MSTFA) gave very good GC-MS properties of the derivatized compounds and provided reliable structural information for their confirmation analysis. This is the first published report on the use of a GC-MS method for the detection of the enantiomers of moprolol and their metabolites in human urine.