Optimization of separation and determination of moxifloxacin and its related substances by RP-HPLC

A RP-HPLC method for the separation and determination of impurities of moxifloxacin, in its pharmaceutical forms as well as moxifloxacin degradation products, was developed with the aid of DryLab ® software and chemometric (response surface) approach. The separation of four synthesis-related impurities was achieved on a Waters C 18 XTerra column using a mobile phase of (water + triethylamine (2%, v/v)): acetonitrile = 90:10 (v/v%); the pH of water phase being adjusted with phosphoric acid to 6.0. Flow rate of the mobile phase was 1.5 ml/min and UV detection at 290 nm was employed. The column was thermostated at 45 °C. The resolution between the two least resolved impurity peaks was in average, R s,min > 1.5. Method validation parameters indicate linear dynamic range 0.2–2.0 μg/ml with LOQ ca. 0.20 μg/ml and LOD ca. 0.05 μg/ml for all analytes. The method was applied for the impurities determination in drug tablets and infusion (Avelox ®, Bayer AG) and for degradation products determination in a stability study of moxifloxacin. The impurity content in the tablets and infusion was quantified as 0.1% of total drug. Two degradation products were noted under hydrolytic conditions. The method can also be used for rapid and accurate quantification of moxifloxacin hydrochloride in its tablets during stability testing.