Determination of sitagliptin in the presence of its organic impurities using Box-Behnken experimental design for robustness assessment

A simple HPLC method was developed and validated for the quantitative determination of sitagliptin and its organic impurities from the synthesis process. The method was carried out in an XBridgeTM Phenyl column (250 mm X 4.6 mm i. d., 5 μm) with a mobile phase consisting of an acetonitrile/formic acid (0.05% aqueous solution) mixture (40:60, v/v), with isocratic elution. Flow rate was 1.0 mL/min and detector wavelength was 207 nm. The validation process, in accordance with international guidelines, shows that the method was linear (R2 = 0.9997-0.9999) and ANOVA showed a non-significant linearity deviation (p>0.05). Precision RSD was <4% (n=6) and method accuracy ranged between 97.52-102.85%. Limits of detection (1.4 and 0.5 μg mL-1) and quantification (2.8 and 2.1 μg mL-1) were determined for impurities 1 and 2, respectively. Critical factors were selected to examine method robustness with a three-level Box Behnken experimental design and no significant factors were detected. The HPLC method for impurity determination in sitagliptin was precise, accurate and robust. The separation of the compounds presented an adequate resolution even in the presence of the main degradation product proving to be effective for routine analyses in the pharmaceutical industry.