Application of Factorial Design and Study of Photodegradation Kinetics for the Determination of Sitagliptin by Capillary Electrophoresis

A quick, reliable micellar electrokinetic chromatography (MEKC) method was developed and validated for the analysis of sitagliptin phosphate in tablets. Separation was carried out in fused silica capillary (48.0 cm total length and 40.0 cm effective length, 50 μm i.d.) by applying a potential of 30 kV (positive polarity), hydrodynamic injection by 50 mbar for 5 s and the temperature of the capillary cartridge was 25 °C. The selected electrolyte consisted of 50 mM TRIS (pH 10.6) to which 75 mM SDS was added (direct UV/PDA detection at 207 nm). The method was validated in terms of specificity, linearity, precision, accuracy and robustness. The method was linear (r = 0.9990) at a concentration range of 50.0 to 150.0 μg mL-1, precise (intra-day relative standard deviation [RSD] and inter-day RSD values < 2.0%), accurate (mean recovery = 101.0%), specific and robust. Moreover, the Plackett-Burman experimental design was used to evaluate robustness, producing results within the acceptable range. The photodegradation kinetics of the drug was evaluated and could be best described as second order kinetics (R2= 0.9838). This proposed method was successfully applied to the quality control analysis of sitagliptin, emphasizing thus the advantages of the method: high efficiency and resolution, rapid analysis and low consumption of sample and reagents.