Characterization of seven new related impurities and forced degradation products of tetracaine hydrochloride and proposal of degradation pathway by UHPLC-Q-TOF-MS.

A rapid and highly sensitive method was developed for separation and identification of the related impurities and degradation products in tetracaine hydrochloride by ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS). The chromatographic separation was achieved on an Agilent Infinity Lab Poroshell 120 EC-C18 column (4.6 ×100 mm, 2.7 µm) using gradient elution with mobiles phase of A (10 mM ammonium acetate buffer containing 0.1% formic acid) and B (acetonitrile) at a flow rate of 1.0 mL/min. Forced degradation experiments were also performed under acidic, alkaline, thermal, photolytic, and oxidative stress conditions following ICH guidance. The result revealed that tetracaine hydrochloride is extremely sensitive to oxidation condition and highly sensitive to alkaline/acidic hydrolysis, and susceptible to light condition. In total, five related impurities and seven degradation products were successfully detected in the positive mode of electrospray ionization. The structures of all these impurities were characterized based on the high-resolution MS data and manufacture process, and the fragmentation pathways of tetracaine and these impurities were constructed and discussed. Seven of them have not been reported before, and two of them were specified impurities described in various pharmacopoeias. The fragmentation pathways and plausible mechanisms for the formation of these impurities were proposed.