Isolation and Characterization of An Allergic Dimer Impurity in Cefmenoxime Hydrochloride by NMR and HR-MS Method

Background: We systematically characterized an allergic dimer impurity in cefmenoxime hydrochloride raw material by UV, IR, HR-MS, 1D, and 2D NMR for the first time. Methods: The dimer stock solution of cefmenoxime hydrochloride was obtained by the degradation method. The target dimer impurity in the stock solution was separated by preparative RP-HPLC and purified by the freeze-drying method. By comparing the dimer to cefmenoxime hydrochloride, the functional groups corresponding to the characteristic peaks of UV and IR spectra were identified, and the molecular formula and mass fragmentation pattern were determined using HR-MS. Results: Then, based on the full assignment of 1H and 13C NMR signals， the dimerized position was confirmed and its absolute configuration was identified by 1D and 2D NMR. Conclusion: This study provided a structural basis for the allergic study of dimer impurities in cephalosporin drugs.