Table 1. Specification and operating condition of GC for propionic acid analysis

Device	Parameter	Condition
GC	Column	HP-FFAP (0.32 mm i.d. × 30 m, 0.25 µM)
	Oven temperature program	60°C (4 min) → 115°C(28°C/min) → 240°C(20°C/min, 5 min)
	Inlet temperature	200°C
	Injector temperature	200°C
	Injection volume	1 µL
	Split ratio	Splitless
	Carrier	Helium, 1.0 mL/min
MS	Ionization mode	Electron ionization (EI)
	Electron impact mode	70 eV
	Selected ion (m/z)	741), 57, 45
	MS ion source temperature	200°C

Quantitation ion.
GC, gas chromatography; MS, mass spectrometry.