Spectrophotometric and Titrimetric Determination of Ciprofloxacin Based on Reaction with Cerium (IV) Sulphate

ABSTRACT: One titrimetric and two spectrophotometric methods are described for the determination of ciprofloxacin in bulk drug and in formulations using cerium (IV) sulphate as the oxidimetric agent and methyl orange and indigo carmine as chromogenic agents. In titrimetry (method A), ciprofloxacin is treated with a measured excess of cerium (IV) sulphate in acid medium and the unreacted oxidant is back titrated with standard ammonium ferrous sulphate using ferroin indicator. In spectrophotometric methods, ciprofloxacin is treated with a known excess of cerium (IV) sulphate and the residual oxidant is determined by treating with a fixed amount of either methyl orange, and measuring the absorbance at 520 nm (Method B) or indigo carmine, and measuring the absorbance at 610 nm (Method C). In all the three methods, the amount of cerium (IV) sulphate reacted corresponds to the amount of ciprofloxacin. Titrimetry is applicable over 2-12 mg range and in the spectrophotometric methods, calibration curves are linear over the concentration ranges of 0.5-3.5 µg ml-1 (method B) and 1.0-7.0 µg ml-1 (method C). The methods were satisfactorily applied to the determination of ciprofloxacin in tablet and injection formulations and no interferences from excipients were noticed