Development of a liquid chromatography/tandem mass spectrometry assay for the quantification of lisinopril in human plasma

A simple and sensitive liquid chromatography/tandem mass spectrometry method employing electrospray ionization, to quantify lisinopril in human plasma using pseudoephedrine hydrochloride as the internal standard (IS), has been developed and validated. A mixture of methanol and 0.1% formic acid in water (50:50, v/v) was used as the isocratic mobile phase. A simple liquid-liquid extraction procedure was used as sample preparation method. The method validation demonstrated the specificity, lower limit of quantification, accuracy, and precision of measurements. Selected reaction monitoring was specific for lisinopril and pseudoephedrine hydrochloride; no endogenous materials from blank plasma interfered with the analysis of lisinopril or the IS. The assay was linear over the concentration range 0.78-100 ng/mL. The correlation coefficients for the calibration curves ranged from 0.9984-0.9998. The intra- and inter-day precision, determined for quality control samples, were less than 4.18%. The method was employed in a pharmacokinetic study after oral administration of 10 mg lisinopril to 20 healthy volunteers.