Exploration and Detection of Nitrosamine Impurity Nitroso-STG-19 in Sitagliptin Tablet and API as well as Nitrites in Excipients by LC-MS/MS Methods

Abstract

Food and Drug Administration (FDA) recently reported a new nitrosamine impurity in sitagliptin that was named as Nitroso-STG-19 (NTTP), whose acceptable intake limit was extremely low at 37 ng per day. Besides, NTTP was found to be a degradation impurity in sitagliptin tablet, which was formed by the reaction of 3-(Trifluoromethyl)-5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-A]pyrazine hydrochloride and nitrite salts introduced via excipients. Consequently, NTTP content in tablets was larger than that in API. To control the impurity, an ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) procedure for the detection of NTTP in both sitagliptin phosphate tablet and active pharmaceutical ingredient (API) was developed and validated. Furthermore, a derivatization method for the detection of nitrite salts at lower concentration was developed to select applicable excipients to decelerate the generation of NTTP. During validation of the analytical procedure for NTTP, quantitation limit (LOQ) of NTTP was 56 ppb (0.056 ng/mL), linear correlation coefficient was 0.9998, and recoveries of NTTP in spiked samples ranged from 95.5% to 105.2%, indicating the method is rapid, sensitive and accurate for NTTP test. In the nitrite salts detection method, LOQ was 0.21 ng/mL, recoveries of NTTP in spiked samples ranged from 87.6 % to 107.8%, indicating a sensitive and accurate method and it was suitable for screening appropriate pharmaceutical excipients.