Determination of the Related Substances of Linagliptin by HPLC

OBJECTIVE To establish an HPLC method for the determination of related substances linagliptin. METHODS The analysis was performed on C₁₈ column by using a gradient method starting with mobile phase composed of phosphate buffer(sodium dihydrogen phosphate 2.0 g dissolved with 1 000 mL waters, adjusted by phosphate to the pH of 2.5±0.1): methanol and acetonitrile(55∶45) at the flow rate of 1.0 mL·min^-1 and the detection wavelength was set at 226 nm. RESULTS The related substances were completely separated from the main peak. The calibration curve were linear, the impurity A in range from 0.59 μg·mL^-1 to 5.91 μg·mL^-1(r=0.999 9), the impurity B in range from 0.59 μg·mL^-1 to 5.86 μg·mL^-1(r=0.999 8), the purity C in range from 0.58 μg·mL^-1 to 5.79 μg·mL^-1(r=0.999 5) and linagliptin from 1.32 μg·mL^-1 to 13.22 μg·mL^-1(r=0.999 7). The average recoveries of the impurity A, the impurity B and the impurity C mentioned above were 99.12%(RSD=2.9%), 99.35%(RSD=2.4%) and 98.52%(RSD=1.1%), respectively. CONCLUSIONS The HPLC method has been developed for quality control, and detection of related substances of linagliptin with high sensitivity and specificity.