Department of Instrumental Analysis, Box 65. Jinling Hospital, Nanjing 210002, The Peoples Republic of China A simple and sensitive reversed-phase liquid chromatographic method has been developed and validated for the analysis of captopril in human plasma and the study of the pharmacokinetics of the drug in human body. Captopril was stabilized by forming an adduct with p-bromophenacyl bromide. The adduct formed and 4-chloro-2-nitroaniline (internal standard) were extracted with ethyl acetate:benzene (l:l), and then measured by HPLC using a Spherisorb C18 column as stationary phase and a water:acetonitrile: acetic acid mixture (44:55:0.2, V/V/V) as mobile phase. Captopril was quantified by absorbance at 258nm. The method proved to be linear in the clinical range of 5-500 nglmL. The lower limit of detection of captopril in plasma was 2 nglmL. Intra-day and inter-day coefficients of variation of assay for captopnl in plasma were 5.8%-8.5% (n=7) and 8.0%-9.5% (n=5), respectively. The recoveries of captopril were 90%-98% for plasma. The data obtained was fitted with 3PS7 program on computer to study the pharmacokinetics. The results showed that the disposition of captopril was conformed to a two-compartment open .model with T,,,,,=O.S6 h, C,,=266.5 ng/mL andAUC,,=3803 ngh/mL. The method has been used to determine captopril in plasma samples from ten volunteers and provided data on the pharmacokinetics of the drug. The results inferred that captopril is absorbed rapidly and had a relatively short half-life time in healthy individuals.