Analysis of the polymerized impurities in cefmetazole sodium based on novel separation principle by liquid chromatography tandem ion trap/time-of-flight mass spectrometry

To effectively control the polymerized impurities in cefmetazole sodium, novel high performance gel filtration chromatography (HPSEC) with TSK-gel G2000SWxl column and RP-HPLC method with C18 column were used in replace of classical gel filtration chromatography with Sephadex G-10 gel. By studying the chromatographic behavior of polymerized impurities in both chromatographic systems with different chromatographic separation principles, the polymerized impurities in cefmetazole sodium were separated and detected effectively. The two-dimensional liquid chromatography tandem ion trap/time-of-flight mass spectrometry (2D LC-IT-TOF MS) was applied to characterize the structures of polymerized impurities eluted from HPSEC method, and liquid chromatography tandem ion trap/time-of-flight mass spectrometry was applied to characterize the structures of polymerized impurities and other unknown impurities eluted from RP-HPLC method. The structures of fourteen unknown impurities in cefmetazole sodium were deduced based on the MS n data, nine of which were polymerized impurities. The corresponding relationship between impurities in the HPSEC method and RP-HPLC method was established, and the specificity of the two methods was evaluated. The RP-HPLC method for analysis of the polymerized impurities has higher column efficiency and specificity than the HPSEC method. The RP-HPLC method is suitable for quality control of the polymerized impurities in cefmetazole sodium. The forming mechanisms of degradation impurities in cefmetazole sodium were also studied.