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Validated Spectrophotometric Methods For The Assay Of Ciprofloxacin In Pharmaceuticals Based On Redox And Complexation Reactions

K.Basavaiah, P.Nagegowda

Two simple and senitive spectrophotometric methods for the determination of ciprofloxacin in pharmaceuticals were developed and validated using cerium(IV)sulphate as the oxidimetric reagent, and orthophenanthroline and thiocyanate as complexing agents. The methods involved the addition of a measured excess of cerium(IV)sulphate to ciprofloxacin in acid medium followed by determination of the residual oxidant by the different approaches. In the first procedure (method A), the residual oxidant was reduced by a known and fixed amount of iron(II), and the unreacted iron(II) was complexed with orthophenanthroline at a raised pH, and the absorbance measured at 510 nm. In the second approach (method B), the residual cerium (IV) was treated with a fixed amount of iron(II), and the resulting iron(III) was complexed with thiocyanate and the absorbance measured at 470nm. In both methods, the amount of cerium(IV)sulphate reacted corresponded to the amount of ciprofloxacin. The Beer’s law was obeyed over the concentration ranges of 1.0-8.0 μg/ml (method A) and 0.5-4.0 μg/ml (method B). The calculated molar absorptivities were 6.10 x 104 and 4.26 x 104 l/mol/cm for method A and method B, respectively, and the respective limits of detection were 0.12 and 0.065 μg/ml. The methods were satisfactorily applied to the determination ciprofloxacin in tablets and no interference from excipients was observed. The validity of the methods was further ascertained by parallel assay by an established method, and by recovery studies.