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.