Photometric Determination of Roxithromycin and Midecamycin

Brown colored compound was formed between the antibiotics roxithromycin (or midecamycin) and dil.H2SO4,with absorption maxima at the wavelength 482 nm,and molar absorptivity (ε) of 5.00×103L·mol-1·cm-1 for roxithromycin (1.02×104L·mol-1·cm-1 for midecamycin).Linear relationship between values of absorbance and concentration of the antibiotics was obtained in the range within 17.0 mg·L-1 for roxithromycin (in the range within 20.5 mg·L-1 for midecamycin).Based on these facts,a photometric method for determination of the antibiotics was proposed,and its feasibility was proved by analyzing substantial drug tablets.