Dvb car pdms

The SPME fibre was 50/30 μm DVB/CAR/PDMS which length was 1 cm (Sigma-Aldrich, Shanghai, China), and the fiber penetration depth into the headspace was 2 cm. The size of the extraction bottle was 15 mL.
When extracting aroma substances, a tea sample (5.0 g) was placed in an extraction bottle, which was equilibrated in a thermostatic water bath for 10 min at 80 °C and then sampled for 30 min in the head space. After that, SPME fiber was then withdrawn and directly introduced to the GC–MS, and the process was repeated 3 times.

Shanghai OE Biotech Co., Ltd. completed untargeted metabolome sequencing. HS-SPME extracted VACs from pepper fruit samples: Fruit samples are frozen fresh fruit and were immediately powdered with a grinder (MM400, Retsch, Dusseldorf, GER), then defrosted at room temperature prior to analysis. Accurately weigh the 1 g of sample powder and add to an ethanol solution containing 20 μg/mL n-alkanes (C7–C40) as an internal standard (configuration method: 980 μL ethanol solution (99.7%) + 20 μL n-alkanes mother liquor (1 mg/mL)) and then transfer to a sealed headspace injection bottle (20 mL, Agilent, Santa Clara, CA, USA) for the release of volatiles. The headspace bottle was equilibrated at a temperature of 60 °C and a shaking speed of 450 rpm for 10 min. Then the extraction head (50/30 μm DVB/CAR/PDMS, Sigma, Shanghai, China) was inserted into the headspace part of the sample and extracted for 60 min [52 (link),53 (link)].

A solid phase microextraction (SPME) fiber holder (57330-U, Sigma-Aldrich) containing fiber coated with divinyl benzene/carboxen/poly dimethyl siloxane 50/30 µm (DVB/CAR/PDMS) (57328-U, Sigma-Aldrich) was used for absorption of volatile compounds from the headspace of pathogens. To provide conditions that increase the rate of VOC absorption, after incubation time, 2ml of NaCl 36% was added to each culture. Then the DVB/CAR/PDMS fiber was suspended from the top of the bottle containing the culture and placed on a magnetic stirrer hotplate at 70°C for 30 minutes
^{30 (link)}. After that, the fiber was placed at the injection site of GC-MS and all the absorbed VOCs entered the device. Eventually each VOC is represented as a chromatogram peak in the monitor that is connected to the GC-MS. For thermal desorption, the SPME fiber remained in the injector for 2 minutes before it was exposed to the headspace of the pathogen samples
^{31 (link)}. To avoid possible false discoveries each state was tested at least three times.

An aliquot (2 mL) of chokeberry juice was pipetted into 20 mL headspace glass vial containing 1 g ammonium sulfate. Subsequently, 10 μL of an internal standard solution (1,4-dioxane 1000 mg/L) was added. The vials were sealed with crimp caps with PTFE-lined silicone septa and equilibrated for 5 min at 40 °C under stirring at 250 rpm in a water bath. The volatiles were extracted by exposing the (solid-phase microextraction) SPME fiber (DVB/CAR/PDMS, length 2 cm, Sigma Aldrich, Germany) for 30 min under the same conditions.

Hexanal was extracted using solid-phase microextraction (SPME). Samples of walnut grounded (3 g ± 0.1 g), spiked with 4-methyl-2-pentanol as internal standard (2.5 mg/kg), was weighed into a 20 mL glass vial and sealed with a PTFE/silicone septum (Agilent Technologies, Palo Alto, CA, USA). After 10 min in agitation mode, at 40 °C, a solid-phase microextraction (SPME) fiber (DVB/CAR/PDMS, Sigma-Aldrich, St. Louis, MO, USA) was exposed to the sample headspace for 40 min for volatile extraction. The hexanal analysis was performed in triplicate using a GC system (Agilent Technologies, Palo Alto, CA, USA) that comprise an autosampler (Agilent PAL RSI 85), a gas chromatograph (GC Agilent 7820A), and a mass spectrometer (Agilent 5977B) that included an electron impact source and a quadrupole analyzer. A Supelcowax 10 (30 m × 0.25 mm × 0.25 μm, Sigma-Aldrich, St. Louis, MO, USA) was used for compounds separation. Helium was used as carrier gas at a flow rate of 1 mL/min. GC oven temperature started at 40 °C and ramped at 3 °C/min after 10 min to the final temperature of 200 °C. The data were recorded and analyzed using Agilent MassHunter Qualitative Analysis. Hexanal was identified using the NIST 08 Mass Spectral Library and via comparison with the standard (Sigma-Aldrich, St. Louis, MO, USA).

(GC-MS) analysis GC-MS-QP2020 (Shimadzu Corp., Kyoto, Japan) measurements were analyzed as previously described [16 (link),18 (link)], which is a modification of a previous method [19 (link)]. Briefly, samples were added to a 20 mL headspace vial and warmed for 5 min at 60 °C. A solid-phase microextraction (SPME) fiber of 50/30 µm DVB/CAR/PDMS (Sigma-Aldrich, Tokyo, Japan) was inserted into the vial, and the components were extracted for 30 min at 60 °C. The SPME fiber was then inserted into a single quadrupole GC–MS system with a GCMS-QP2020 gas chromatograph and an AOC-6000 autosampler (Shimadzu, Kyoto, Japan). The analysis conditions were as follows: carrier gas, helium (constant pressure 150 kPa); row, DB-Heavy WAX 0.25 mm × 60 m, 0.25 µm (Agilent Technologies, CA, USA); vaporization chamber, split 1 min at 250 °C; temperature program, 50 °C for 4 min, with temperature then being increased by 5 °C/min increments and maintained at 250 °C for 15 min; MS conditions, scan range 30–400 m/z; ionization potential, 70 eV; ion source, 200 °C; and transfer line, 250 °C. Both extraction and injection were performed once. Compounds in the obtained particle spectra were estimated using the main EI-MS library software of the NIST/EPA/NIH Mass Spectral Library with Search Program 2017 (NIST17).

A series of C8–C22 n-alkanes (Sigma-Aldrich-St. Lois, MO, USA) was used for the determination of the 1D linear temperature programmed retention indices (LTPRI), additionally hexane and heptane were used in order to calculate with high precision minors alkanes. The HS-SPME procedures were performed using a SPME fiber coated with 50/30 µm divinylbenzene/Carboxen on poly(dimethylsiloxano) (DVB/CAR/PDMS) (Sigma-Aldrich). Septum-sealed Pyrex vials of 20.00 mL (Wheaton science Products-Millvine, NJ, USA), volumetric flask of 50.00 mL and magnetic stirrers were also used during the sample preparation procedures (Sigma-Aldrich).