An improved HPLC method with the aid of a chemometric protocol: simultaneous analysis of amlodipine and atorvastatin in pharmaceutical formulations

Statistical experimental design and Derringer's desirability function were applied to develop an improved RP-HPLC method for the simultaneous analysis of amlodipine and atorvastatin in pharmaceutical formulations. Four independent factors were considered: acetonitrile content in the mobile phase; buffer pH; buffer concentration; and flow rate. The preliminary screening step was carried out, according to a 2(4-1) fractional factorial design, to identify the significant factors affecting the analysis time response. Then central composite design was applied for a response surface study, in order to examine in depth the effects of the most important factors. Subsequently, Derringer's desirability function was employed to simultaneously optimize the six responses: retention factor of first peak; two resolutions; and three retention times, each having a different target. This procedure allowed deduction of two separate optimum conditions, intended for the analysis of quality control and plasma samples, within the experimental domain. The predicted optimum for the quality control samples was: methanol-acetonitrile-15 mM K(2)HPO(4) buffer (pH 5.33) (10:42.08:47.92, v/v/v) as the mobile phase and 1.12 mL/min as the flow rate. The method using this optimized condition showed higher sensitivity and shorter analysis time than the previously published reports. The optimized assay condition was validated according to International Conference on Harmonization guidelines.