Development and validation of a capillary electrophoresis method with laser-induced fluorescence detection for the determination of captopril in human urine and pharmaceutical preparations

This study describes the development of a CE method for the analysis of the antihypertensive drug captopril using LIF detection. The method is based on the derivatization of captopril with the fluorescent label 5‐iodoacetamidofluorescein. The optimization of the electrophoretic electrolyte composition together with other variables, such as applied voltage and injection time, resulted in a solution of 20 mM phosphate buffer adjusted to pH 12.0. The calibration curve for the fluorescent captopril derivative was linear in the concentration range 3.5–6000 ng/mL with a detection limit of 0.5 ng/mL. Intra‐ and interday precision (at a concentration of about 100 times the LOD) were less than 0.86 and 1.16%, respectively, both expressed as RSD. The assay was successfully used for quantification of captopril in some marketed pharmaceutical preparations and urine samples.