Quadruple Response Factorial Design Optimization of Capillary Zone Electrophoresis Assay Procedure for Metformin and Sitagliptin Combination

The metformin-sitagliptin combination has been recently approved in 2012 for its better efficacy and safety for diabetes than using single drugs. The current manuscript describes an assay method for this recent combination by capillary zone electrophoresis (CZE). The factorial design optimization of electrolyte composition for quadruple response of resolution, migration time, peak area, and peak symmetry was conducted. The univarite method was applied for optimizing other electrophoretic conditions. The optimum electrolyte composition was 10mM borate at pH 6.4. Sufficient separation with a resolution of 6.7 and peak symmetry of 0.932 and 0.985 were obtained. Satisfactory repeatability of migration time, peak area, peak height, and peak symmetry (RSD 0.16-2.4%) was obtained. The validation parameters were acceptable in terms of recovery, linearity, inter-mediate precision, limits of detection, and limits of quantification. The use of CZE provides reagent-saving and fast method comparing with reported HPLC methods.