Three simple, rapid and accurate spectrophotometric methods were developed for the simultaneous determination of moxifloxacin hydrochloride and difluprednate in ophthalmic eye drop formulation using methanol as solvent. Method 1 is the simultaneous estimation method and both the drugs exhibit good linearity over the concentration range of 4 to 12 μg/ml for moxifloxacin and 0.4 to 1.2 μg/ml for difluprednate at λmax of 291.0 and 237.0 nm, with regression coefficient 0.9993 and 0.9953 respectively. Method 2 is the second order derivative method, where moxifloxacin and difluprednate showed zero cross over point at 240.0 and 252.6 nm respectively. Beer’s Lambert’s law was obeyed over the concentration range of 4 to 12 μg/ml for moxifloxacin and 1 to 12 μg/ml for difluprednate with regression coefficient 0.9991 and 0.9945. Method 3 is the ratio second derivative method, and at 275.20 and 249.40 nm, linear concentration range for moxifloxacin and difluprednate was 4 to 10 μg/ml and 4 to 20 μg/ml with regression coefficient 0.9976 and 0.9952 respectively. The methods were validated according to ICH guidelines for evaluation of accuracy, precision, repeatability, reproducibility, sensitivity etc. The proposed procedures can be successfully applied for the determination of moxifloxacin and difluprednate in eye drops, for routine quality control analysis.
