Captopril is an angiotensin-converting enzyme commonly used to treat high blood pressure and to improve survival after a heart attack. Considering the importance of the assay of this drug, the authors propose a simple and costeffective colorimetric technique for its quantitative determination. The detection strategy was based on the redshift of the surface plasmon resonance band of silver nanoparticles (AgNPs) induced by the action of captopril molecules. Under optimal experimental conditions, the interaction of AgNPs with captopril molecules in the presence of barium ions induces the aggregation of AgNPs.
