Ultra‐high‐performance liquid chromatography‐tandem mass spectrometry analytical method for the determination of nitrosamine drug substance‐related impurity in sitagliptin base and salts

A reversed‐phase ultra‐high‐performance liquid chromatography‐tandem mass spectrometry method is presented for the quantification of the mutagenic impurity 7‐nitroso‐3‐(trifluoromethyl)‐5,6,7,8‐tetrahydro‐[1,2,4]triazolo[4,3‐a]pyrazine found in three sitagliptin drug substances (sitagliptin base [SG], sitagliptin hydrochloride monohydrate [SG HCl{H}] salt, and sitagliptin phosphate monohydrate [SG P{H}] salt). A simple and highly sensitive method was developed for SG, SG HCl(H) salt, and SG P(H) salt. Sample preparation was adapted to each product considering solubility, sensitivity, and accuracy issues. Chromatographic separation was achieved using an Acquity HSS T3 column (3.0 × 100 mm, 1.8 μm) and a mobile phase consisting of formic acid 0.1% in water combined with methanol. Detection and quantification of the impurity were carried out using triple quadrupole mass spectrometry detection with electrospray ionization in the multiple reaction monitoring mode. The limit of detection and limit of quantification was found to be 0.1–0.3 and 10 ppb, respectively. The accuracy and precision of the method were satisfactorily determined with recovery values between 74.1% and 119.4%. Linearity is demonstrated in the range of 10 and 2000 ppb with regression coefficients (R) within the range of 0.9918–0.9972. The method is currently used for the analysis of the mutagenic impurity in the three‐drug substances in the Moehs Group.