Table 1.

Specific parameters for metabolomic studies.

	GC/MS	LC-QTOF-MS 1	LC-QTOF-MS 2
Instruments	Shimadzu GCMS-QP2010 (Ultra, Kyoto, Japan)	ACQUITY UPLC H-Class System, Xevo G2-XS-Quadrupole-Time of Flight system (Waters Corporation, USA)	Exion LC AD System, TripleTOF®5,600-Quadrupole/Time-of-Flight system (AB SCIEX LLC., Redwood City, CA, USA).
Columns	Rtx-5 MS capillary column (0.25 μm, 0.25 mm × 30 m; Restek, PA, USA)	Amide XBridge UPLC column (3.5 μm, 4.6 mm × 100 mm; Waters Corporation, USA)	Kinetex C18 column (2.6 μm, 100 mm × 2.1 mm; Phenomenex, Torrance, CA, USA)
Injection volume	0.5 μl	10 μl	10 μl
Chromatographic conditions	Split mode (split ratio 8:1); injector temperature 250°C; septum purge flow rate 6 ml/min; carrier gas flow rate 1.5 ml/min. Column temperature gradient: 0–5 min, 80°C; 5–16 min, 80°C−300°C; 16–21 min, 300°C	Flow rate 0.4 ml/min; column temperature 40°C; autosampler temperature 4°C. Mobile phase: 0.1% formic acid (solvent A), acetonitrile (solvent B). Solvent gradient: 0–3 min, 85% B; 3–6 min, 85–30% B; 6–15 min, 30–2% B; 15–18 min, 2% B; 18–19 min, 2–85% B; and 19–26 min, 85% B	Flow rate 0.4 ml/min; column temperature 40°C; autosampler temperature 4°V. Mobile phase: 0.1% formic acid (solvent A), acetonitrile (solvent B). Solvent gradient: 0–1 min, 10–30% B; 1–19 min, 30–95% B; 19–20 min, 95% B
Mass spectrometry conditions	Electron impact (EI) ion source; ion source temperature 220°C; ionization electron beam 70 eV; full scan mode, m/z 50–700; run time 19 min, solvent cutting acquisition time 4.5 min	Electrospray ionization (ESI) ion source; positive ion mode, gas 1 pressure 50 psi, gas 2 pressure 30 psi, curtain gas 30 psi; ion spray voltage 4,500 V; turbo spray temperature 500°C; full scan m/z 50–1,000, product ions m/z 50–900; declustering potential (DP) 100 V, collision energy (CE) 35 eV	Electrospray ionization (ESI) ion source; positive and negative ion modes; information-dependent acquisition (IDA) criteria; ion spray voltage +5,500/−4,500 V; turbo spray temperature 550°C; nebulizer gas pressure 55 psi; heater gas pressure 55 psi; curtain gas pressure 35 psi; DP ±80 V; CE 35 eV; mass range m/z 60–1,000
Data pre-processing software	Shimadzu GC Postrun Analysis	Progenesis QI (Waters Corporation, USA)	Analysis Base File Converter, MSDIAL ver.4.70
Metabolite identification	National Institute of Standards and Technology (NIST) library 2.0 (2008); Wiley 9 (Wiley-VCH Verlag GmbH & Co. S5 KGaA, Weinheim, Germany); Standard compound self-built library (CPU library, China Pharmaceutical University, China)	Human Metabolome Database (HMDB), METLIN, Chemspider, CPU library	MSMS-Public-Pos-VS15, MSMS-Public-Neg-VS15 (matching MSDIAL), CPU library
Normalization method	IS normalization	IS normalization	LOWESS regression