Db 5 column

The GC-MS analysis of EOs was carried out on a Thermo Scientific TRACE 1310 Gas Chromatograph attached with ISQ LT single quadruple Mass Spectrometer, equipped with DB-5 column (30 m × 0.32 mm, i, d., 0.25 μm film thickness, J&W Scientific). The ionization mode is EI with electron ionization energy of 70 eV. The temperature of the column was programmed from 40°C to 275°C at 5°C/min. The injector and detector temperatures were the same at 300°C. Helium was used as the carrier gas at a flow rate of 1.0 ml/min. The identification of the chemical compounds was based on mass spectra (Wiley 275.L, 8th edition mass spectral library), or with standards when available, and confirmed by comparison of their GC retention indices either with those of standards or with data published in the literature as described by Adams (2007) [22 ].

Metabolites in the cecal contents were analyzed by GC/MS-TQ8040 (Shimazu, Kyoto, Japan) with a BPX-5 column (30 m × 0.25 mm i.d.; film thickness 1.00 μm, Trajan Scientific and Medical, Vic., Australia) for short chain fatty acids (SCFAs), and a DB-5 column (30 m × 0.25 mm i.d.; film thickness 1.00 μm, J&W Scientific Inc, Folsom, CA, USA) for other previous described metabolites [12 (link)]. Mass spectrum peaks were detected using GCMSsolution software (Shimazu), and the retention time correction of peaks was performed based on the retention time of a standard alkane series mixture (C9 to C33). Metabolites were detected by Smart Metabolites Database (Shimazu) which registered 12 spectrums for BPX-5 column and 475 spectrums for DB-5 column.

Based on a previous study28 (link), GC-TOF-MS analysis was performed with an Agilent 7890 gas chromatograph system linked to a Pegasus HT time-of-flight mass spectrometer (LECO, St. Joseph, MI, USA). The system employed a DB-5 column with 5% diphenyl and 95% dimethyl polysiloxane (J&W Scientific, Folsom, CA, USA). The GC column temperature was programmed to rise from 50 to 330 °C at a rate of 10 °C/min. One microliter of sample was injected in splitless mode. The energy was −70 eV in electron impact mode. Data were acquired in full-scan mode with an m/z range of 30–600 at a 20 spectra/sec velocity.

Manure volatile analyses were carried out on a gas chromatograph (Focus GC, Thermo, USA) coupled to a single quadrupole mass spectrometer (Thermo DSQ II, USA). The MS parameters used were as follows: electron impact ionization energy 70 eV and an m/z range from 41 to 300, and the spectra were collected at 6 scans/sec. The GC was equipped with a split/splitless injection port with an SPME glass liner (1 mm ID x 120 mm straight long, ThermoFischer, USA) and a DB5 column (30 m × 0.25 mm × 0.25 μm; J&W Scientific, Folsom, CA, USA) with helium carrier gas (1.2 ml min^–1). The injection port was maintained at 250 °C, and the SPME fiber was left extended in a splitless state for 5 min before the injector split was activated. After desorption, the fiber remained in the injector port for another 3 min. The oven temperature was programmed to start at 60 °C for 1 min, increase by 5 °C min^–1 to 250 °C and then hold at this last temperature for 15 min. The transfer line temperature was 280 °C. Xcalibur software (Thermo Fisher) was used for data processing and reporting of GC-MS analyses. Target compounds were identified by comparing their mass spectra with those in the Wiley 275L library and matching their retention times and mass spectra to those of authentic standards.

The QFFs and PUF plugs spiked with surrogate standards were extracted with a Soxhlet extractor using 150 ml dichloromethane for 48 h. The extract was rotary-evaporated to about 2 ml and solvent-exchanged to hexane, and then 4 ml concentrated sulfuric acid was added. Each extract was subsequently cleaned with a gel permeation chromatography column (40 g Bio-Beads SX-3). The final extract volume was evaporated to 100 μL under a gentle N₂ stream. Internal standards were added before instrumental analysis.
PBDEs congeners were quantified with a Shimadzu GCMS-QP 2010 plus instrument with the selective ion monitoring (SIM) mode. A DB-5 column (15 m × 0.25 mm × 0.1 μm, J&W Scientific) was employed. The analysis of PBDEs congeners using the isotope internal standard method followed our previous study[18 ].

A headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) system was used to determine carvacrol and overall volatile profile in the fruit samples following the previous method [16 (link)]. Briefly, 4 blueberries (about 8 g), cut in to 4 pieces of each, were sealed in a 20-mL glass vial; a 2-cm SPME fiber (50/30 μm DVB/Carboxen/PDMS; Supelco, Bellefonte, PA) was inserted in the vial to extract the headspace volatiles for 60 min at 40 °C. Volatiles were separated by a DB-5 column (60 m × 0.25 mm i.d., 1.00 μm film thickness; J&W Scientific, Folsom, CA, USA) equipped GC, and identified by a MS detector (GC-MS, Model 6890, Agilent, Santa Clara, CA, USA). The concentration of residual carvacrol in blueberries was calculated using a standard curve with four levels (2 ng L⁻¹ to 2 mg L⁻¹) of standard carvacrol dissolved in acetone.

Oxidized sterol derivatives were analyzed on a Hewlett-Packard 6890 gas chromatograph equipped with a DB-5 column (30 m × 0.25 mm × 0.25 μm; J&W, Folsom, CA). Samples were injected in a splitless mode and the column temperature programmed as follows: an initial temperature of 160 °C was held for 1 min, then programmed at 40 °C min⁻¹ to 270 °C and held for 1 min; further programmed at 4 °C min⁻¹ to 280 °C, final temperature was held for 25 min. A hydrogen carrier gas flow of 1 mL min⁻¹ was used. Oxysterols were identified using retention data for previously verified compounds by mass spectrometry utilizing our library and published data [24 (link)]. Samples from autonomous series were analyzed in triplicate.