Quantitative determination of the angiotensin-converting enzyme inhibitor lisinopril in human plasma by stable isotope dilution gas chromatography/negative ion chemical ionization mass spectrometry.

A simple, highly accurate and precise method for the quantitative measurement of the angiotensin-converting enzyme inhibitor lisinopril in human plasma is presented. The assay is based on gas chromatography/negative ion chemical ionization mass spectrometry. The preparation of stable isotope labelled lisinopril for use as an internal standard is described. The method involves solid phase extraction on C18 sorbent and derivatization to the methyl diester-trifluoroacetamide derivatives. The detection limit was found to be 50 pg and a lower limit of quantification was reached down to 0.5 ng/mL plasma.