Tg 5silms gc column

For GC/MS–MS analysis 1 µl of the samples was injected with a splitless liner in a Trace 1310 Gas Chromatograph (Thermo Fisher Scientific Inc., Waltham, MA, USA) and analytes were separated on a TG-5SILMS GC column (15 m × 0.25 mm × 0.25 μm) (Thermo Fisher Scientific Inc., Waltham, MA, USA). Helium as carrier gas was used with a carrier flow rate of 1.5 ml/min and a split flow rate of 20 ml/min. The oven temperature program was as follows: 1 min at 120 °C, heating to 220 °C with a heating rate of 30 °C/min, heating to 300 °C with a heating rate of 50 °C/min up to 300 °C, 300 °C held for 0.5 min. The retention times for TNT, 4-ADNT, 2-ADNT and 2,4-DA-6-NT were 3.50 min, 4.32 min, 4.50 min and 4.64 min, respectively. Eluted analytes were ionized with electron ionization (EI) or negative chemical ionization (CI) with methane as the reagent gas and analyzed with a TSQ 8000 EVO Triple Quadrupole Mass Spectrometer (Thermo Fisher Scientific Inc., Waltham, MA, USA) in MRM-mode.

VOCs were first adsorbed by solid-phase microextraction (SPME) (Supelco, 57329-U). The VOCs adsorbed above were then analyzed by a TSQ8000 mass spectrometer (Thermo Fisher). Briefly, a fused-silica fiber coated with divinylbenzene (DVB), carboxen (CAR), and polydimethylsiloxane (PDMS) was traversed into the sampling headspace bottle via a silicone septum. After adsorption at 40°C for 60 min, the fiber was inserted into a GC injector to desorb the volatile compounds at 250°C for 5 min. The released components were then separated by a TG-5SILMS GC column (Thermo Fisher, 30 m × 0.25 mm × 0.25 μm). The carrier gas of the GC was helium, and the gas flow rate was 1.3 mL per min. The temperature program in the GC oven consisted of 40°C for 2.0 min, raising to 100°C at 3°C per min and then to 240°C at 20°C per min, 240°C for 5.0 min. The electron ionization (EI) applied was fixed at 70 eV, and the ion source temperature used in the MS was set at 230°C. The m/z scan range was 40–400 amu. The results obtained above were searched against the database of the National Institute of Standards and Technology (NIST).

Polar metabolites were extracted as previously described with few modifications (Cerna et al., 2017 (link)) and measured using a Q Exactive GC Orbitrap GC-tandem mass spectrometer and Trace 1300 Gas chromatograph (Thermo Fisher). Samples were injected using the split mode (inlet temperature 250°C, splitless time 0.8 min, purge flow 5.0 ml/min, split flow 6.0 ml/min) onto TG-5SILMS GC Column (Thermo Fisher, 30 m × 0.25 mm × 0.25 μm) with helium as a carrier gas at a constant flow of 1.2 ml/min. Metabolites were separated with a 28 min gradient (70°C for 5 min followed by 9°C per min gradient to 320°C and finally 10 min hold time) and ionized using the electron ionization mode (electron energy 70 eV, emission current 50 μA, transfer line and ion source temperature 250°C). The MS operated in the full scan mode, 60000 resolution, scan range 50–750 m/z, automatic maximum allowed injection time with automatic gain control set to 1e6, and lock mass [m/z]: 207.0323. Data were analyzed by TraceFinder 4.1 with Deconvolution Plugin 1.4 (Thermo) and searched against NIST2014, GC-Orbitrap Metabolomics library and inhouse library. Only metabolites fulfilling identification criteria (score ≥ 75 and ΔRI < 2%) were included in the final list.