GC-MS Analysis of Volatile Compounds

(GC-MS) analysis GC-MS-QP2020 (Shimadzu Corp., Kyoto, Japan) measurements were analyzed as previously described [16 (link),18 (link)], which is a modification of a previous method [19 (link)]. Briefly, samples were added to a 20 mL headspace vial and warmed for 5 min at 60 °C. A solid-phase microextraction (SPME) fiber of 50/30 µm DVB/CAR/PDMS (Sigma-Aldrich, Tokyo, Japan) was inserted into the vial, and the components were extracted for 30 min at 60 °C. The SPME fiber was then inserted into a single quadrupole GC–MS system with a GCMS-QP2020 gas chromatograph and an AOC-6000 autosampler (Shimadzu, Kyoto, Japan). The analysis conditions were as follows: carrier gas, helium (constant pressure 150 kPa); row, DB-Heavy WAX 0.25 mm × 60 m, 0.25 µm (Agilent Technologies, CA, USA); vaporization chamber, split 1 min at 250 °C; temperature program, 50 °C for 4 min, with temperature then being increased by 5 °C/min increments and maintained at 250 °C for 15 min; MS conditions, scan range 30–400 m/z; ionization potential, 70 eV; ion source, 200 °C; and transfer line, 250 °C. Both extraction and injection were performed once. Compounds in the obtained particle spectra were estimated using the main EI-MS library software of the NIST/EPA/NIH Mass Spectral Library with Search Program 2017 (NIST17).