[Spectrophotometry determination of roxithromycin based on charge transfer reaction].

A spectrophotometric method for the determination of Roxithromycin has been developed based on the charge transfer reaction between Roxithromycin as donor and cresol red as acceptor. The conditions of reaction have been studied. The reaction time, reaction temperature, reaction medium and the concentration of reagent was ten min, 35 degrees C, alcohol-acetone solution and 6 x 10(-4) mol.L-1 respectively. The apparent molar absorptivity of complex was 1.05 x 10(4) L.mol-1.cm-1 at 456 nm. The Beer's law was obeyed in the range of 0-80 mg.L-1 of Roxithromycin with correlation coefficient 0.9997. The recovery was over 98%. The composition of the charge transfer complex between Roxithromycin and cresol red was 1:1. The reaction mechanism has been discussed based on the composition of the complex. The present method has been applied to the determination of Roxithromycin in capsules with satisfactory results.