Determination of roxithromycin by spectrophotometry based on thymol blue charge transfer reaction

An UV-Vis spectrophotometric method for determination of roxithromycin was developed based on the charge transfer reaction between roxithromycin as the donor and thymol blue as the acceptor in alcohol medium. The experimental results showed that roxithromycin reacted with thymol blue to form an 1∶1 complex at room temperature, the apparent molar absorptivity of the complex was 1.70×10³ L·mol⁻¹·cm⁻¹ at 438nm, the stability constant was 1.53×10⁶, and the linear range of the determination was 41.9∼419 mg·L⁻¹.