Multivariate optimization of a capillary zone electrophoresis assay method for simultaneous quantification of metformin and vildagliptin from a formulation

A rapid, accurate, precise, and optimized capillary zone electrophoresis assay was established and validated for the simultaneous quantification of metformin and vildagliptin in tablets. The electrophoretic separation was achieved on an untreated bonded silica capillary with a background electrolyte comprising 25 mM of borate buffer at pH 7.5 at 207 nm. The concentration of the buffer and the pH of BGE were optimized using the multivariate optimization method for determining the retention time and peak area. Furthermore, the sample injection time, capillary oven temperature, and applied voltage were optimized. The capillary zone electrophoresis technique was validated for all required parameters as per the International Conference on Harmonization recommendations. The linearity ranged in the concentrations of 5–500 µg/mL and 5–100 µg/mL with the limit of detections of 0.22 µg/mL and 0.40 µg/mL for metformin and vildagliptin, respectively. In addition, the percent relative standard error for repeatability and inter-day precision was within the acceptable range. The mean recoveries determined by the capillary zone electrophoresis method were 99.2% and 100.4% for metformin and vildagliptin, respectively. Finally, the capillary zone electrophoresis process was effectively used for the assays of metformin and vildagliptin in their solid dosage form, and statistical outcomes were in agreement with the outcomes of the previously validated RP-HPLC method.