Determination of ifenprodil in human plasma using liquid chromatography coupled with electrospray tandem mass spectrometry

A method for the determination of ifenprodil levels in human plasma was established. Ifenprodil and the internal standard (IS), ketoconazole, were extracted from the plasma with ethyl acetate using liquid-liquid extraction. The extracts were separated by high performance liquid chromatography (HPLC), using the mobile phase of methanol-6 mmol/L ammonium acetate (90:10, v/v) (pH value was adjusted to 7.40). The electrospray ion source was applied and operated in a positive ion mode under the selected reaction monitoring mode with a transition of m/z 326.1→308.2, for quantification of ifenprodil, and m/z 531.0→82.1 for IS. The liquid chromatography-tandem mass spectrometry method provided excellent sensitivity and selectivity for quantification and identification of ifenprodil at low levels, within a run time of 6.0 min. The assay was linear over the range from 0.25 to 50 μg/L. The relative standard deviations for the intra-day and inter-day precision were less than 2.7% and 6.5%, respectively. The average recoveries varied between 101.3% and 105.0%, and the detection limit was 0.08 μg/L. Because of its simplicity and accuracy, the established method is suitable for clinical application in the determination of ifenprodil in human plasma.