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Updated: Aug 18, 2026

Profiling of Methyltransferases and Other S-adenosyl-L-homocysteine-binding Proteins by Capture Compound Mass Spectrometry CCMS
Published on: December 20, 2010
Investigation of nirmatrelvir epimerization occurred in analytical sample solution by using high resolution LC-MSn,
Lewei Zheng1, Lingqiao Wang1, Dan Li1
1Center of Excellence for Modern Analytical Technologies (CEMAT) Huahai Pharmaceutical Co., Ltd, Xunqiao, Linhai, Zhejiang 317024, PR China.
Abstract:
During the related substances testing of nirmatrelvir, an unknown peak was observed and the level of the peak increased over time during the storage of the sample solution. By using a strategy including LC-PDA/UV-MSn analysis, the degradant was rapidly identified as an epimer of nirmatrelvir, a solution degradation product that is caused by the trace amount of alkaline impurities leaching from the glass HPLC vials. In addition, by using hydrogen/deuterium exchange NMR spectroscopy analysis, the epimerization position was determined to be the carbon α to the adjacent cyano group. Further investigation indicated that the occurrence of the solution degradation can be suppressed when the glass HPLC vials were replaced by plastic HPLC or mass spectrometric grade vials.
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