liquid chromatography–tandem mass spectrometry (lc-ms) methodfor the assignment of enalapril and enalaprilat in human plasma

A rapid and sensitive liquid chromatography–tandem mass spectrometry (lc-ms)method was developed for the determination of enalapril and enalaprilat in humanplasma. detection of analytes was achieved by tandem mass spectrometry withelectrospray ionization (esi) interface in positive ion mode which was operated underthe multiple-reaction monitoring mode. sample pretreatment was involved in a onestepprotein precipitation (ppt) with per chloric acid of plasma. the reconstitutedsamples were chromatographed on c18 column by pumping methanol: water: acidformic 74:24:2 (v/v) at a flow rate of 0.2 ml/min. each plasma sample waschromatographed within1.25 min. the standard curves were found to be linear in therange of 0.1–20 ng/ml of enalapril and enalaprilat with mean correlation coefficient of≥0.999 for each analyte. the intra-day and inter-day precision and accuracy resultswere well within the acceptable limits. the limit of quantification (loq) was 0.1ng/mlfor enalapril and enalaprilat. the lower limit of detection (lod) was 0.08 ng/ml forenalapril and enalaprilat.