Stability indicating HPLC method for the simultaneous analysis of Gatifloxacin and Loteprednol in eyedrop formulation using design of experiment approach

Design of experiment (DOE) assisted simple, rapid, precise and accurate stability indicating HPLC method has been developed for simultaneous estimation of Gatifloxacin (GTF) and Loteprednol (LOT) along with their forced degradation products. The developed method has been optimized and developed by using central composite design (CCD) in response surface methodology (RSM). Trails have been undertaken and ratio of phosphate buffer in mobile phase, pH of buffer and flow rate are selected as factors. Resolution, tailing factor (GTF) and tailing factor (LOTE) are selected for determining the system response in the process of method optimization. The responses have been optimized using the Derringer’s desirability function. The effective separation is achieved on Phenomenex EVO-C18 column (250 mm x 4.6 mm i.d, 5 μm particle size) with mobile composed of 10 mM phosphate buffer, pH 3.5 and organic phase composed of mixture of acetonitrile and methanol 60:40 % v/v, the flow rate was 1.0 mL/min, the signals were detected at 267 nm. The developed method was validated for linearity, accuracy, precision, and robustness. The method was applied successfully for stability samples.