Titrimetric and spectrophotometric assay methods for ciprofloxacin in Pharmaceuticals based on neutralization reaction

摘要

Four simple, rapid and reliable methods using visual titrimetric, pH metric, conductometric and spectrophotometric techniques are described for the determination of ciprofloxacin as bulk drug and in commercial formulations. The methods are based on the neutralization reaction involving the carboxyl group of ciprofloxacin and sodium hydroxide in aqueous medium. Visual titrimetry involves the addition of a measured excess of sodium hydroxide to ciprofloxacin followed by back titration of residual basewith hydrochloric acid using bromothymol blue-phenol red mixed indicator, hi pH-metry and conductometry, ciprofloxacin solution is titrated directly with sodium hydroxide, the end-point being determined by pH and conductance measurements. In spectrophotometry, ciprofloxacin is treated with phenol red - sodium hydroxide mixture and change in absorbance is measured at 560 nm and related to ciprofloxacin concentration. Calculations in titrimetry are based on a 1:1 reaction stoichiometry (ciprofloxacin: sodium hydroxide) and 6-20 and 10-60 mg ranges can be determined by visual and graphical methods end-point determination, respectively, hi spectrophotometric method, Beer's law is obeyed over a concentration range 5 - 25ug ml~(-1) with an apparent molar absorptivity of 6.32 x 10~3 1 mol~(-1) cm~(-1) and a Sandell sensitivity of 0.052 ug ml~(-2). The limits of detection and quantification are calculated to be 0.42 and 1.41ug ml~(-1), respectively. Validation parameters for intra-day and inter-day precisionand accuracy are in conformity with the ICH guidelines. The methods were successfully applied to the determination of ciprofloxacin in tablets. The accuracy and validity of the methods were further ascertained by parallel determination by a reference method and by recovery studies.