Determination of azatadine in human plasma by liquid chromatography/tandem mass spectrometry

A sensitive method using liquid chromatography with tandem mass spectrometric detection (LC–MS/MS) was developed and validated for the analysis of antihistamine drug azatadine in human plasma. Loratadine was used as internal standard (IS). Analytes were extracted from human plasma by liquid/liquid extraction using ethyl acetate. The organic phase was reduced to dryness under a stream of nitrogen at 30 °C and the residue was reconstituted with the mobile phase. 5 μL of the resulting solution was injected onto the LC–MS/MS system. A 4.6 mm × 150 mm, I.D. 5 μm, Agilent TC-C18 column was used to perform the chromatographic analysis. The mobile phase consisted of ammonium formate buffer 0.010 M (adjusted to pH 4.3 with 1 M formic acid)/acetonitrile (20:80, v/v) The chromatographic run time was 5 min per injection and flow rate was 0.6 mL/min. The retention time was 2.4 and 4.4 min for azatadine and IS, respectively. The tandem mass spectrometric detection mode was achieved with electrospray ionization (ESI) iron source and the multiple reaction monitoring (MRM) (291.3 → 248.2 m/z for azatadine, 383.3 → 337.3 m/z for IS) was operated in positive ion modes. The low limit of quantitation (LLOQ) was 0.05 ng/mL. The intra-day and inter-day precision of the quality control (QC) samples was 8.93–11.57% relative standard deviation (RSD). The inter-day accuracy of the QC samples was 96.83–105.07% of the nominal values.