INDIRECT SPECTROPHOTOMETRIC DETERMINATION OF NEOMYCIN BASED ON THE REACTION WITH CERIUM (IV) SULFATE

A simple and sensitive spectrophotometric method has been described for the assay of neomycin either in pure form or in pharmaceutical formulations. The proposed method was based on the oxidation of the studied drug by a known excess of cerium (IV) sulfate in acidic medium and estimating the unreacted oxidizing agent by adding a known amount of methyl orange in the same acid medium and measuring the absorbance of the resulted solution at λmax=498 nm. Different variables affecting the reaction were studied and optimized. Beer’s law is obeyed in the concentration range of 1 10-6 and 1.3 10-5 M and the detection limit of the method was 4.7 10-7 M neomycin. The proposed method was applied successfully to the determination of the examined drug either in a pure or pharmaceutical dosage forms with good precision. No interferences were observed from excipients and the results obtained were in good agreement with those obtained using the official method.