High-performance liquid chromatography–electrospray ionization mass spectrometry method for the measurement of moclobemide and two metabolites in plasma

A rapid and sensitive liquid chromatography–electrospray ionisation mass spectrometry (HPLC–ESI-MS) assay has been developed for the measurement of moclobemide and metabolites, Ro12-5637 and Ro12-8095, in human plasma. Sample preparation (0.5 ml plasma) involves solid-phase extraction using C₁₈ cartridges. A Nova-Pak phenyl column (Waters, 4 μm, 150×2 mm I.D.) was employed for analyte separation with a mixture of 0.2 M ammonium formate buffer, pH 3.57 and acetonitrile as the mobile phase. The within- and between-day precisions of the assay were <18% and the limit of quantification for all analytes was 0.01 μg/ml. The total run-time was 6 min. The method described was used to measure moclobemide, Ro12-5637 and Ro12-8095 in human plasma following an oral 300 mg dose.