Determination of Captopril in some Pharmaceutical products

A simple, inexpensive, rapid and more sensitive batch and flow injection spectrophotometric methods for determination of captopril in pharmaceutical products. The procedure was based on oxidation of captopril with a known excess of bromine solution in acid medium. Bromine solution in acid medium bleaches the methyl red dye. A known excess of bromine in acidic medium treated with captopril is reduced to bromine, the unreacted bromine which is remaining is decolered by methyl red dye. The dyes showed maximum absorption at 515 nm. Beer's law was obeyed in the concentration ranges 0.2-2.0 mig mL-1 with detection limits 0.008 mig mL-1 . The molar absorptivity and correlation coefficients (r) were 1.63x105 l/mol.cm, 0.9995 for batch method. The calibration graph constructed for FI method, obeyed Beer's law in the concentration range (1-5 mig mL-1 ) with a limit of detection 0.25 mig mL-1 , molar absorptivity 2.3x104 l/mol.cm, correlation coefficient (r) 0.999, , and sampling rate 128 determinations per hour.