SPECTROPHOTOMETRIC DETERMINATION OF SOME FLUOROQUINOLONE DERIVATIVES THROUGH OXIDATION WITH CERIUM (IV)

Document Type : Original Article

Author

Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Assiut University, Assiut, Egypt

Abstract

A simple, rapid and sensitive spectrophotometric method is described for the determination of the fluoroquinolones; amifloxacin, difloxacin, norfloxacin, ofloxacin, ciprofloxacin, pefloxacin and lomefloxacin. The method is based on their oxidation with cerium (IV) ammonium sulphate in 4 M perchloric acid and subsequent measurement of the residual cerium (IV) via its reaction with p-Dimethylaminobenzaldehyde (p-DMAB) to give a reddish colored product to be then measured at 463 nm. The method obeys Beer's Law over a general concentration range of 0.5-12 µg/ml. Accuracy and precision of the method were checked. Molar ratio determination to the reaction with norfloxacin, as an example, indicates 1:12 (drug to Ce (IV)) and 1:4 (p-DMAB to Ce (IV)) ratios, respectively. A good negative correlation is found between the molar absorptivities of the reacted compounds with their pK2 (piperazine moiety). Mechanism of reaction between each of fluoroquinolones and p-DMAB with Cerium (IV) was studied. The proposed procedure was applied for the assay of dosage forms containing fluoroquinolones without interference from common additives. Interference from sodium ascorbate present in peflacine ampoules is eliminated by its oxidation with 1 ml 0.1% potassium bromate solution before applying the proposed procedure.

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