Sensitive high-performance liquid chromatographic method for determination of captopril in plasma

A rapid, simple and sensitive high-performance liquid chromatographic method for the determination of captopril in plasma has been developed. Captopril is derivatized with a new reagent, 2-bromo-2'-acetonaphthone to form a product that showed ultraviolet-absorbing properties. For plasma samples, the protein was removed with 6% perchloric acid and the derivatized captopril was extracted with diethyl ether. The chromatographic separation was performed on an analytical mu bondapak NH2 column (300 x 3.9 mm, i.d.) with an isocratic mobile phase consisting of n-hexane-2-propanol-methanol-acetic acid (68:15:15:2). Using ultraviolet detection at 246 nm, the quantification limit for captopril in plasma was 10 ng/ml. The calibration curve was linear over the concentration range 12.5-500 ng/ml. The average recovery was 95% for plasma. The inter-day and intra-day assay coefficients of variation were found to be less than 12%.