RAPID ANALYSIS OF LABETALOL IN HUMAN PLASMA USING LIQUID CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY

A simple and sensitive liquid chromatography–tandem mass spectrometry method was developed and validated for estimation of Labetalol in human plasma, an adrenergic β-receptor blocking agent used in the treatment of hypertension, which exhibits both α- and β-adrenoreceptor blocking activity. The analyte and internal standard (Metoprolol) were extracted by liquid/liquid extraction with ethyl acetate. The chromatographic separation was performed on reverse phase Phenomenax Luna column (C18, 5µm, 100 x 4.6 mm) with a mobile phase of 2 mM ammonium formate (pH 5.0) / methanol (20:80 v/v), which was pumped at a flow rate of 0.5 mL / min with split ratio of 20:80. The protonated analyte was quantitated in positive ionization by multiple reactions monitoring with a mass spectrometer. The mass transitions m/z 329.01→161.95 and 267.99→115.86 were used to measure Labetalol and Metoprolol, respectively. The lower limit of quantitation was 3.1800 ng/mL with a relative standard deviation of less than 15%. Acceptable precision and accuracy were obtained for concentrations over the calibration curve ranges (3.1800 to 700.8760 ng/ml). Sample analysis time of 2.5 min for each sample made it possible to analyze a throughput of more than 400 human plasma samples per day.