5975c inert xl

The essential oil (EO) of Lavandula luisieri was analysed by Gas Chromatography-Mass Spectroscopy (GC-MS) using an Agilent 7890 GC coupled with an Agilent 5975 C inert XL mass selective detector (MSD), operated in the electron impact EI mode (electron energy = 70 eV), scan range = 50–500 amu, and scan rate = 3.99 sans/sec), and an Agilent ChemStation data system. The separation conditions included a DB-5MS fused silica capillary GC column, constituted by a (5% phenyl)-polymethylsiloxane as stationary phase, film thickness of 0.25 mm and an internal diameter of 0.25 mm. The carrier gas was helium, and the column head pressure was 48.7 kPa and a flow rate of 1.0 mL/min. Temperature profile: injector temperature, 250 °C; oven initial temperature, 60 °C for 5 min; temperature rise, 10 °C/min until 250 °C. The GC was operated with an injection volume of 1 mL and a split ratio of 1:50. The identification of components was ascertained by comparison of the retention times and mass spectra with those of the pure standard compounds. All mass spectra were also compared with those of the data system library NIST and Wiley.

Clostridium thermocellum switchgrass fermentation samples were measured at 19, 43, 91, and 187 h, as matched for proteomic samples. Frozen cell pellets containing both microbe and plant material were weighed into 50 ml centrifuge tubes containing 10 ml of 80% ethanol, and 50 µl sorbitol (0.01000 g/ml) added as an internal standard. Samples were sonicated for 5 min (30 s on, 30 s off with an amplitude of 30%) and kept on ice. Samples were then centrifuged at 4500 rpm for 20 min, and the supernatant was decanted into scintillation vials and stored at −20 °C. One milliliter per sample was dried down, dissolved in 0.5 ml acetonitrile, and silylated to generate trimethylsilyl derivatives, as described elsewhere [21 (link)]. After 2 days, 1 µl aliquots were injected into an Agilent 5975C inert XL gas chromatograph–mass spectrometer (GC–MS). The standard quadrupole GC–MS was operated in the electron impact (70 eV) ionization mode, targeting 2.5 full-spectrum (50–650 Da) scans per second, as described previously [21 (link)] (see Additional file 1: Text S1 for additional details regarding metabolites quantification). Metabolite data were expressed as fold change relative to the 19-h sampling time point with significant differences determined with Student’s t tests. Significant differences in fold change between sampling time points were also assessed with Student’s t tests.

GC-MS was carried out on all samples using an Agilent 7890 A Series chromatograph attached to an Agilent 5975 C Inert XL mass-selective detector with a quadrupole mass analyser (Agilent technologies, Cheadle, Cheshire, UK). A splitless injector was used and maintained at 300 °C. The carrier gas used was helium, and inlet/column head-pressure was constant. The column (DB-5 ms) was coated with 5% phenyl-methylpolysiloxane column (30 m × 0.250 mm × 0.25 μm; J&W Scientific, Folsom, CA, USA). The oven temperature was set at 50 °C for 2 min, then raised by 10 °C min⁻¹ until 325 °C was reached, where it was held for 15 min until the end of the run. The GC column was inserted directly into the ion source of the mass spectrometer. The ionisation energy of the mass spectrometer was 70 eV and spectra were obtained in scanning mode between m/z 50 and 800. The MS was also used in selected ion monitoring (SIM) mode with the oven temperature set at 50 °C for 1 min, then raised by 20 °C min⁻¹ until 280 °C, then raised at 10 °C min⁻¹ until reaching 325 °C, where it was held for 10 min until the end of the run. In SIM mode, a first group of ions (m/z 189, m/z 204, m/z 231, m/z 425, m/z 440) corresponding to miliacin fragmentation were monitored. After 16 min, a second group of ions (m/z 57, m/z 71, m/z 85, m/z 478, m/z 506) were monitored to record the internal standard.

A total of 28 yeast-derived aroma compounds (esters, higher alcohols, terpenes, C6 alcohols, and fatty acids) were measured using headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME GC-MS) (Malherbe et al. 2009 (link), Herbst-Johnstone et al. 2013 (link), Pinu et al. 2014 , Parish et al. 2016 (link)). Each sample was incubated for 10 minutes in the Gerstel MultiPurpose Sampler VT32-20 and agitated at 500 rpm prior to extraction. A 2 cm, 23-guage, 50/30 μm, DVB/CAR/PDMS fibre was exposed to the sample for 60 minutes at 45°C. After extraction, the fibre was transferred to the rear injection port of an Agilent 7890A GC system coupled to a mass selective detector model 5975C inert XL. Helium was used as the carrier gas at a low rate of 1 ml/min. Volatile compounds were separated on a tandem column composed of an Agilent HP-1 ms and an Agilent HP-INNOWax. Agilent MassHunter Quantitative Analysis software was used to quantify the resulting peaks via integration. The integration values were compared to standards to determine the concentration of volatile compounds (μg/l) in each sample.

GC-MS analyses were performed in a gas chromatography equipment (model 7890A, Agilent Technologies, CA, USA) coupled to a single quadrupole mass spectrometer detector (model 5975C inert XL, Agilent Technologies). The separation was carried out in a HP-5MS column (30 m length, 0.25 mm i.d., with 0.25 mm film composed of 95% dimethyl/ 5% diphenylpolysiloxane, Agilent Technologies). Helium was used as carrier gas at 1.0 mL/min flow rate. The GC injector was maintained at 250°C and samples were injected with 1:10 split, 10 mL/min of He was used. The temperature gradient was: initial oven temperature 60°C for 1 min, increased to 300°C at 10°C/min, following by cooling to 60°C in 1 min and maintained for 5 min. The run time was 25 min. The temperatures of the transfer line of the detector, filament source, and the quadrupole were maintained at 290, 230 and 150°C, respectively. The electron ionization source was -70 eV energy. The MS was operated in scan mode in the range 50–600 m/z. The software Mass Hunter B.07.01 (Agilent Technologies) was used for operation and data acquisition.