Abstract: Objective To explore the fragmentation pathway of dipyridamole compounds under the electrospray ionization mass spectrometry (ESI-MS), so as to provide a reference for the identification and structural analysis of these compounds. Methods A Shim-packXR-ODS (100 mm×2.0 mm, 2.2 μm) column was used for secondary mass spectrometry (MS/MS) analysis of dipyridamole (nisoldipine, nifedipine, nimodipine, nitrendipine, nicardipine, felodipine, amlodipine) in positive ion mode with a gradient elution of 0.1% formic acid solution (A) - 0.1% formic acid acetonitrile (B) as the mobile phases, ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and the fragmentation behaviors of dipyridamole were summarized. Results The constituents of dipyridamole were easy to be protonated in the positive ion detection mode, forming quasi-molecular ions of [M+H]⁺. The dipyridamole compounds had similar cleavage pathways, and the fracture process in the positive ion mode mainly focuses on the ester groups near the parent nucleus of the dihydropyridine or the substituents on the benzene ring, forming specific ionic fragments (m/z 315.097 7, m/z 195.090 8, and m/z 165.080 2). That is, the mother ion removes one molecule of the esterification group - OR, and then loses the neutral fragment to replace the phenyl. On this basis, another molecule of the esterification group - OR is lost, forming a mother nucleus derived form of 1,4-dihydropyridine. These ion fragments can intuitively represent the substituent groups on the parent nucleus, thereby further reflecting the molecular structure of dipine drugs. Conclusion The electrospray mass spectrometry cleavage pattern proposed in this paper can help to analyze and deduce the structure of diphenhydramine compounds, which can provide a reference basis for the identification and structural analysis of these components.

Key words: dipyridamole compounds, dihydropyridine, UPLC-Q-TOF-MS, cleavage pattern, identification, structural analysis