[Determination of ifenprodil in human plasma using liquid chromatography 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 methanol-6 mmol/L ammonium acetate (pH value was adjusted to 7.40) (90 : 10, v/v) as the mobile phase, and were then detected using mass spectrometry (MS). Electrospray source was applied and operated in positive ion mode. Selected reaction monitoring (SRM) mode with the transition of m/z 326.1 --> 308.2 was used to quantify ifenprodil, and m/z 531.0 --> 82.1 for IS. The excellent sensitivity and selectivity of the HPLC-MS/MS method allowed quantitation and identification of ifenprodil at low levels with a run time of 6.0 min. The assay was linear over the range from 0.25 to 50 microg/L. The intra-day and inter-day precisions measured as relative standard deviations (RSDs) were less than 2.7% and less than 6.5%, respectively. The average recoveries varied between 101.3% and 105.0%, and the detection limit was 0.08 microg/L. Due to its simplicity and accuracy, the established method is suitable for the application in a pharmaceutical study of the intervenous drop infusion of ifenprodil tartrate.