Determination of Captopril in Blood and Urine by High-Performance Liquid Chromatography

A new procedure has been established for the determination of captopril [1-(D-3-mercapto-2-methyl-1-oxopropyl)-L-proline] in biological fluids. Captopril was trapped with p-bromophenacyl bromide or N-(4-dimethylamino-3, 5-dinitrophenyl) maleimide (DDPM), then the addition products were separated and determined by high-performance liquid chromatography (HPLC) on a reversed-phase column. The disulfides, metabolic products derived from captopril and excreted in the urine, were reduced with tributylphosphine to captopril which in turn was trapped with DDPM. These adducts were separated and determined by HPLC. The method provided quantitative results for captopril levels of 5-2000 ng/ml of whole blood and 0.1-100μg/ml of urine with satisfactory accuracy and precision.