Department of Chemistry, Faculty of Science, University of Aleppo, Aleppo, Syria Tel: (963)(944)814291; E-mail: antakli@scs-net.org

We carried out a new spectrophotometric method in order to determine captopril drug which is used as antihypertensive in tablet form. The method is based on the reduction of Fe³⁺ to Fe²⁺ by captopril, the resulting Fe²⁺ reacts with 1,10-phenanthroline to give a soluble orange-red complex in acidic medium. The maximal absorption is at the wavelength 510 nm. The linear relationship between the absorbance and the concentration of captopril was in the range of 1-35 mg/L with a correlation coefficient R² = 0.999. The detection limit is 1 mg/L, the molar absorption coefficient is 11865 L mol^-1 cm^-1. This new method has offered a determination of captopril drug without any interference with excipients or hydrochlorothiazide either in raw material or in tablets indirectly with a high accuracy and an authenticity for the analytical results.