SOLID PHASE EXTRACTION AND HIGH PERFORMANCE LIQUID CHROMATOGRAPHIC DETERMINATION OF ENALAPRIL IN HUMAN PLASMA

A reversed phase high performance liquid chromatographic method utilizing solid phase extraction has been described for the determination of enalapril in human plasma. The C₁₈ sorbent cartridges were conditioned and plasma samples were applied, washed with 20 mmol·L^-1 HCl (2×0.5 ml) and petroleum ether (boiling range 60～90℃) subsequently; and eluted with methanol (3×0.5 ml). The eluent was evaporated to dryness, reconstituted in 100 μl mobile phase and injected. Chromatographic separation was achieved on a Spherisorb C₈ column (200 mm×4.6 mm, 5 μm), with ethanol—water—10% H₃PO₄—triethylamine (30∶70∶1.5∶0.1) at a flow rate of 1.0ml·min^-1. UV detection was set at 215 nm. The calibration ranges were 2.5～150 ng·ml^-1 with regression coefficient of 0.997 and detection limit of 1.5 ng·ml^-1. The within-day RSD and between-day RSD were <8.73%, the recovery of method >91.6%. This method was applied to the pharmacokinetic analysis of enalapril in 8 human volunteers.