Development of a liquid chromatography-mass spectrometry method for monitoring the angiotensin-converting enzyme inhibitor lisinopril in serum.

In this study, a sensitive, specific, precise and accurate method for lisonopril quantitative determination in human serum was developed and validated. The method comprises lisinopril isolation from serum by means of solid-phase extraction followed by its quantification by liquid chromatography-mass spectrometry. Chromatographic separation was performed at 55 degrees C on Kromasil C(18) 5 micrometer 250x3.2 mm HPLC column with mobile phase composed of 50 mM ammonium formate buffer (pH 3)-acetonirile-methanol (72:7:21, v/v/v). A Finnigan AQA benchtop mass spectrometer with a pneumatically assisted electrospray (ES) interface and a single quadrupole mass filter was used to detect and quantify lisinopril in column effluent. Ion signals were acquired by selected ion monitoring of the protonated lisinopril ion m/z=406.5 (M+1). The detector response was linear with r>0.9993 in the investigated concentration range 6-150 ng/ml. The mean recovery of lisinopril from serum samples was 88%. The limit of quantitation for lisinopril was 6 ng/ml with a signal-to-noise ratio at this concentration level S/N=34.75+/-3.9 (n=4).