Spectrofluorimetric analysis of certain macrolide antibiotics in bulk and pharmaceutical formulations

The macrolides (erythromycin, erythromycin esters, azithromycin dihydrate, clarithromycin and roxithromycin) can be analyzed by a simple spectrofluorimetric method based on the oxidation by cerium(VI) in the presence of sulphuric acid and monitoring the fluorescence of cerium(III) formed at lambda(ex) 255 nm and lambda(em) 348 nm. All variables affecting the reaction conditions as cerium(VI), sulphuric acid concentrations, heating time, temperature and dilution solvents were carefully studied. Linear calibration graphs were obtained in the range of 42.6-1200 ng ml(-1) with a percentage relative standard deviation in the range of 0.014-0.058%. Quantitation and detection limits were calculated. The method was applied successfully for the assay of the studied drugs in pure and pharmaceutical dosage forms as tablets, capsules and suspension. Recovery experiments revealed recovery of 98.3-100.8%. The effect of potential interference due to common ingredients as glucose, sucrose, lactose, citric acid, and propylene glycol was investigated. Applying standard addition method shows a recovery of 97.7-100.9% macrolide antibiotics from their corresponding dosage forms.