Determination of quinapril and quinaprilat in human plasma by ultraperformance liquid chromatography–electrospray ionization mass spectrometry

A novel, specific and sensitive ultraperformance liquid chromatography tandem mass spectrometry (UPLC–MS/MS) method was developed for the simultaneous determination of quinapril and its active metabolite quinaprilat in human plasma. The method involves a simple, one‐step extraction procedure coupled with an Acquity UPLC™ BEH C 18 column (100 × 2.1 mm, i.d., 1.7 µm) with isocratic elution at a flow‐rate of 0.2 mL/min and lisinopril as the internal standard. Detection was performed on a triple‐quadrupole tandem mass spectrometer in multiple reaction monitoring mode via electrospray ionization. Using 250 µL plasma, the methods were validated over the concentration range 5.010–500.374 ng/mL for quinapril and 10.012–1000 ng/mL for quinaprilat, with a lower limit of quantification of 5.010 ng/mL for quinapril and 10.012 ng/mL for quinaprilat. The intra‐ and inter‐day precision and accuracy were within 10.0%. The recovery was 85.8, 62.6 and 61.3% for quinapril, quinaprilat and lisinopril, respectively. Total run time was 3.0 min only. Copyright © 2008 John Wiley & Sons, Ltd.