Xcalibur data processing system

The GC-QQQ/MS system comprised of a TRACE 1310 system and TSQ ENDURA mass spectrometer with electron impact (EI) ion source and Xcalibur data processing system and was purchased from Thermo Scientific (Waltham, MA, USA). The GC-QQQ/MS instrument was used to analyze the VOCs of the GFs with a DB-5MS silica capillary column (30 m × 0.25 mm, 0.25 μm). The temperature of the injector was set at 250°C. Helium (99.999% purity) was used as the carrier gas at a flow rate of 1.0 mL/min and a split ratio of 1 : 30. The temperature sequence of the column was programmed as follows: an initial temperature of 50°C held for 2 min, increased at 10°C/min to 200°C then increased to 280°C at 5°C/min and held there for 10 min. The mass detector was equipped with EI, the ionization voltage was set at 70 eV in the 50–550 m/z scan range for the mass spectra collection, and the temperatures of the ion source and mass spectrum transmission line were 280°C.

The UHPLC-MS/MS system consisted of a Thermo Ultimate 3000 system and TSQ ENDURA mass spectrometer using an electrospray ionization (ESI) and X Calibur data processing system (Thermo, USA). Optimized MS parameters were as follows: drying gas temperature, 350°C; ion transport tube temperature, 325°C; gasification temperature, 275°C; atomizing gas pressure, 255 kPa; sheath gas, 35 psi; aux gas, 10 psi; sweep gas, 2 psi; collision voltage, 3500 V; the cracking voltage, 175 V; and the tapered voltage, 65 V. The injection volume was 5 μL, and the total run time was 16.5 min. Some parameters of MRM are shown in Table 1.
The mass spectrometer was operated by the negative multiple reaction monitoring (MRM) mode. Chromatography was achieved on an Ascentis® Express C₁₈ column (5.0 mm × 3.0 mm, 2.7 μm) from Sigma-Aldrich (St. Louis, MO, USA). The gradient elution mobile phase was composed of 0.1% formic acid-purified water in phase A and acetonitrile in phase B. The gradient program was as follows: 0∼2 min, 20%B; 2∼5 min, 20%B⟶35%B; 5∼10 min, 35%B⟶41%B; 10∼13 min, 41%B⟶80%B; 13∼14 min, 80%B⟶20%B; and 14∼16.5 min, 20%B. The flow rate was set at 0.3 mL/min, and the temperature was kept at 35°C.