Determination of moclobemide in human plasma by high-performance liquid chromatography with spectrophotometric detection

A simple and sensitive high-performance liquid chromatographic (HPLC) method with spectrophotometric detection was developed for the determination of moclobemide in human plasma. Plasma samples were extracted under basic conditions with dichloromethane followed by back-extraction into diluted phosphoric acid. Isocratic separation was employed on an ODS column (250 mm×4.6 mm, 5 μm) at room temperature. The mobile phase consisted of 5 mM NaH2PO4–acetonitrile–triethylamine (1000:350:10 (v/v/v), pH 3.4). Analyses were run at a flow-rate of 1.0 ml/min and ultraviolet (UV) detection was carried out at 240 nm. The method was specific and sensitive with a quantification limit of 15.6 ng/ml and a detection limit of 5 ng/ml at a signal-to-noise ratio of 3:1. The mean absolute recovery was about 98.2%, while the intra- and inter-day coefficient of variation and percent error values of the assay method were all at acceptable levels. Linearity was assessed in the range of 15.6–2000 ng/ml in plasma with a correlation coefficient of greater than 0.999. This method has been used to analyze several hundred human plasma samples for bioavailibility studies.