3.5. Mass Spectrometry

Mass spectrometry analysis was performed on a Q-Exactive Plus hybrid quadrupole Orbitrap mass spectrometer (Thermo Scientific, San Jose, CA, USA) equipped with a heated electrospray ionization source (HESI). It was operated in both negative and positive ion modes. The other parameters were set as follows: spray voltage, ±3.5 kV; sheath gas flow rate, 35 arb; auxiliary gas, 10 arb; capillary temperature, 350 °C; auxiliary temperature, 400 °C; S-lens RF level, 60 V. Full Scan/dd-MS² was used to acquire the qualitative data. The resolution for MS and MS/MS was set as 70,000 and 17,500, respectively. The scan range was set as m/z 100–1500, and the normalized collision energies (NCE) were 35%. The five most abundant ions in each full scan were selected as precursor ions to obtain their MS/MS spectra. Data were processed using Xcalibur^TM 4.1 software (Thermo Fisher). For t-SIM scan mode, the accurate [M − H]⁻ or [M + H]⁺ of detected compounds in GDL Pill was added in the Inclusion List to increase the detection sensitivity.