Simultaneous determination of ramipril and its active metabolite ramiprilat in human plasma by LC-MS-MS

A selective, rapid and sensitive liquid chromatography tandem mass spectrometry method has been developed for the simultaneous determination of ramipril and ramiprilat in human plasma using enalapril as the internal standard via one-step extraction with ethyl acetate under acidic condition. The analysis was carried out on a Diamonsil C(18) column (150 mm x 4.6 mm i.d., 5 mu m) with a mobile phase consisting of 1% formic acid-acetonitrile (25:75, v/v) at a constant flow rate of 0.5 mL min(-1). The detection was performed on a triple-quadruple tandem mass spectrometer by selective reaction monitoring mode via electrospray ionization. Linear calibration curves of ramipril and ramiprilat were obtained in the concentration range of 0.107-107.0 and 0.262-105.0 ng mL(-1), respectively. The intra- and inter-day precision (RSD) values were below 8.2 and 4.8% for ramipril, 10.4 and 12.3% for ramiprilat, and accuracy (RE) were within +/- 5.5 and +/- 3.2%, respectively at all QC levels. The method was utilized to support clinical pharmacokinetic studies in healthy volunteers following oral administration of ramipril tablets.