Following a method presented in the literature [25 (link)], experiments were performed on a LECO Pegasus® 4D GC×GC-TOFMS system (LECO Corp., St. Joseph, MI, USA). The column configurations for GC×GC analysis consisted of two columns which were coupled in tandem. The 1D column was a 60 m × 0.25 mm × 0.25 µm DB-FFAP (Agilent Technologies, Palo Alto, CA, USA), and the 2D column was a 1.5 m × 0.25 mm × 0.25 µm Rxi-17Sil MS secondary column (Restek, Bellefonte, PA, USA). Helium was used as the carrier gas at a constant flow rate of 1.0 mL/min. The injector temperature was set at 250 °C. The initial oven temperature was held at 45 °C for 3 min, and then ramped at a rate of 4 °C/min to 150 °C, and held for 2 min, reaching 200 °C at 6 °C/min and 230 °C at 10 °C/min for 20 min. The secondary oven was set at a 5 °C offset, relative to the primary oven. The modulator was set at a 20 °C offset, relative to the primary oven, and a modulation period of 4 s was used. The TOFMS was operated at an acquisition rate of 100 spectra/s and scanned from 50 m/z to 350 m/z.
The detector voltage was set to 1350 V, and the electron energy was −70 V.
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