Simultaneous determination of dexamethasone and moxifloxacin in pharmaceutical formulations using stability indicating HPLC method

A simple, sensitive, specific, precise and accurate stability indicating reverse phase liquid chromatographic method was developed for simultaneous determination of moxifloxacin hydrochloride and dexamethasone in bulk drugs and pharmaceutical formulations. The developed chromatographic method was optimized for the separations of moxifloxacin hydrochloride, dexamethasone and stress-induced degradation products by the use of BDS Hypersil C8 column (250 × 4.6 mm, 5 μm) as stationary phase with mobile phase consisting of a mixture of phosphate buffer (20 mM) containing 0.1% (v/v) triethylamine, at pH 2.8 (adjusted with dilute phosphoric acid) and methanol (38.5:61.5 v/v) at a flow rate of 1.5 mL min−1. Chromatographic separations of analytical peaks and degradation products were achieved within 10 min. Detection of the analytes and degradation products was performed at 254 nm using a diode array detector. Method validation was performed in accordance with ICH guidelines. Linearity of the method was established over the concentration ranges of 50-350 μg mL−1 for moxifloxacin hydrochloride and 10-70 μg mL−1 for dexamethasone (correlation coefficients greater than 0.999). The method resulted in good separation of both the analytes and degradation products with acceptable tailing and resolution with peak purity index ⩾0.9999 which indicated complete separation of analyte peaks from the degradation products. The method can therefore be considered as stability-indicating and can be used successfully for simultaneous determination of moxifloxacin hydrochloride and dexamethasone in pharmaceutical formulations and stability studies.