In a pH 4. 5 Britton-Robinson( BR) buffer solution,propranolol hydrochloride( PRO) can react with Erythrosine B( EryB) to form a 1∶ 1 ion-association complex,which result in the color of EryB fading and the maximum fading wavelength located at 522 nm. The concentration of PRO obeyed Beer's law in the range of0. 15- 6. 24 μg /mL. The molar absorptivity( ε) and detect limit are 4. 85 × 104 L · mol- 1·cm- 1and0. 046 μg /mL,respectively. The method is sensitive,simple,rapid and stable,and it can be applied to t...