Azithromycin (MW 748.98) is a semi-synthetic and 15-membered ring macrolide antibiotic, and mainly used for treatment of respiratory tract infections caused by susceptible bacteria. The full-scan mass spectrum and fragmentation mechanism of azithromycin acquired by MPTDI-TOF MS are shown in Figure 5a and Supplementary Figure S-2a, respectively.Figure 5MPTDI-TOF full-scan mass spectra of (a) azithromycin; (b) oxytetracycline; (c) metronidazole; (d) isoniazid; (e) ribavirin; (f) acyclovir in positive mode