Spectrophotometric Determination of Propantheline Bromide by the Color Reaction of Congo Red

In an HOAc-NaOAc buffer solution of pH 4.04,a red complex,was formed by the reaction of propantheline bromide with congo red,having the absorption maximum at the wavelength of 500 nm.Beer's law was kept in the range of 0.4-40.0 mg· L-1,with detection limit of (3s/k) 0.15 mg·L-1.The conditions of color reaction were tested and optimized.The proposed method was used in the determination of propantheline bromide in pharmaceuticals,giving values of recovery by standard addition method in the range of 98.2%-102.0% and RSD′s in the range of 1.3%-1.6%.The results obtained was in conformity with those by UV-spectrophotometry.