Trace gc ultra apparatus

500 µL of sample were placed in a 2 mL glass-vial with 1 mL of ammonium sulphate solution (45 % w/v) and extracted with 250 µL of methyl acetate-ethanol solution (99.5:0.5, v/v) containing 50 ppm of internal standards (4-methyl 2-pentanol, 1-nonanol, and heptanoic acid). A 3 µL sample of the upper, methyl acetate phase, was injected with the SSL liner held at 180 °C.
Gas chromatography–mass spectrometry was carried out in a Thermo TRACE GC Ultra apparatus equipped with a Thermo TriPlus autosampler with a fused-silica capillary column TG-WAXMS A (30 m long; 0.25 mm OD; 0.25 µm film thickness) coupled to a Thermo ISQ mass detector.
Chromatographic conditions were as follows: 5 min at 40 °C, 3 °C/min up to 200 °C, 15 °C/min up to 240 °C, and 10 min at 240 °C. Helium was used as carrier gas at a flow rate of 1 mL/min, operating in split mode (ratio 30). Detection was performed with the mass spectrometer operating in the Full Scan mode (dwell time 500 ms), with 70 eV ionization energy, and source and quadrupole temperatures of 250 °C. Peaks were identified by comparison of retention times and ion spectra from real standards (Sigma-Aldrich Química) and spectra from the NIST mass spectral library. For each compound, including internal standards, the sum of the areas of the peaks of up to five characteristic ions was obtained.

Commercial LEO from the flowering herb of L. angustifolia Mill. (Lamiaceae) was purchased from Pollena-Aroma (Nowy Dwór Mazowiecki, Poland). The LEO was analyzed by gas chromatography-flame ionization detector-mass spectrometer (GC-FID-MS) at the Institute of General Food Chemistry, Łódź University of Technology, Poland using a Trace GC Ultra apparatus (Thermo Fisher Scientific, Waltham, MA, USA) MS DSQ II detectors, and an FID-MS splitter (SGE, Trajan Scientific Europe, Milton Keynes, UK). Identification of compounds in LEO was based on the comparison of their MS spectra with the MS spectra of computer libraries (MassFinder 3.1, Wiley Registry of Mass Spectral Data, and NIST 98.1 [41 ,42 ,43 ] along with the retention indices on a non-polar column (Rtx-1, MassFinder 3.1, Restek Corporation, Bellefonte, PA, USA) associated with a series of n-alkanes with linear interpolation (C-9 to C-26).
Concentrations of LEO from 500 to 0.12 µL/mL were prepared by dissolving essential oil in Tween 80 (Sigma-Aldrich, Darmstadt, Germany) (1%, v/v) and diluting by Mueller-Hinton broth (MHB, Sigma-Aldrich, Darmstadt, Germany).

Samples with added inositol standard were hydrolyzed with 3 M TFA at 120°C. Monosaccharides were converted to alditol acetates by conventional methods and identified by GC-MS on a Trace GC Ultra apparatus, coupled with a DSQ II Mass spectrometer (Thermo Scientific), and equipped with a TR-5MS capillary column (30 m×0.25 mm ID×0.25 µm film) with helium carrier gas, using a temperature gradient 170°C (3 min), 250°C at 5°C·min⁻¹.