Determination of Roxithromycin by Spectrophotometry Based on the Charge Transfer Reaction with 2,4-Dinitrophenol

In an ethanolic medium, roxithromycin reacted with 2,4-dinitrophenol to form a charge-transfer complex, which showed a maximum absorption peak at 365 nm. Under the optimum condition, linear relationship was found between values of adsorbances and mass concentrations of roxithromycin in the range of 0.006-0.050 g·L-1 with detection limit (3S/N) of 1.8 mg·L-1. The proposed method was used in the determination of roxithromycin in its tablets, giving results in agreement with the labeled value.