Liquid chromatographic-mass spectrometric method for quantitative determination of lisinopril in human plasma

A validated liquid chromatographic-mass spectrometric (LC/MS) method for the determination of lisinopril in human plasma is presented. Enalapril was used as an internal standard. After the addition of internal standard, solid phase extraction was used as a cleaning step. To separate lisinopril and enalapril from interfering endogenous plasma substances, the analysis was performed using column switching valve. The quantitative determination was performed using selected ion monitoring (+)-electrospray LC-MS. A combination of an acidic mobile phase and a reverse phase column was used. A precision in the linear range from 10 to 500.0 ng/mL plasma, absolute recovery of 91.69% for lisinopril and 90.26% for enalapril, stability for 3.5 months at -20 degrees C have been achieved. Limit of quantitation (LOQ) was 10 ng/mL while limit of detection (LOD) was about 1 ng/mL.