Spectrophotometric methods for the determination of gemifloxacin in pharmaceutical formulations

This paper describes two simple spectrophotometric methods for the determination of the antibiotic gemifloxacin mesylate (GFX) in pharmaceutical formulations. The first (A) is an indirect method in which oxidation of the drug with a known excess of cerium (IV) sulphate is followed by determination of the residual oxidant by adding excess methyl orange and measuring residual dye at 507 nm. The second (B) is a derivatisation method involving reaction of GFX with 1,2-naphthoquinone-4-sulphonate (NQS) in alkaline medium (pH 11) to form an orange-coloured product exhibiting maximum absorption (λmax) at 411 nm. The methods were linear in the concentration ranges 2–9 and 5–30 μg/mL for methods A and B, respectively, with intra-day precision (as RSD)