Pdms dvb fibre

The headspace extraction was performed with a manual SPME holder using polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre obtained from Supelco Co. (Bellefonte, PA, USA). The fibre was conditioned prior to the extraction according to the instructions by Supelco Co. For HS-SPME, previously prepared samples (1 g) were placed separately in 5 mL glass vials and hermetically sealed with PTFE/silicone septa. The vials were maintained in a water bath at 60 ^oC during equilibration (15 min) and HS-SPME (45 min). After sampling, the SPME fibre was withdrawn into the needle, removed from the vial, and inserted into the injector (250 ^oC) of the GC-FID and GC-MS for 6 min where the extracted volatiles were thermally desorbed directly to the GC column. HS-SPME was done in triplicate for each sample.

Total Strecker aldehydes content was determined as described by Bueno et al. [10 (link)]. In summary, vials were prepared inside an oxygen free chamber, pouring 10 mL of wine sample into a 20 mL vial. Then samples were spiked with methyl 2-methylbutyrate (187 µg/L) as internal standard and 6 g/L of glyoxal. Vials were then closed and incubated at 50 °C for 6 h for ensuring that carbonyl-bisulphite complexes had been broken. Total isobutyraldehyde, 2-methylbutanal, 3-methylbutanal, methional and phenylacetaldehyde were measured by headspace-solid phase microextraction followed by gas chromatography—mass spectrometry (HS-SPME-GC-MS) using a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre from Supelco (Madrid, Spain).

The cabbage volatile profile was determined by gas chromatography with mass spectrometry (GC-MS) by a solid-phase micro-extraction (SPME) method. The extraction method was based on modified procedure that was described by [16 (link)]. Briefly, the samples were prepared by stirring 5 mL of sample and 1 g of sodium chloride in a sealed vial. After preheating (5 min. at 40 °C) volatiles were collected by SPME for 20 min. at 40 °C using 65 μm PDMS/DVB fibre (Supelco Inc., Bellefonte, PA, USA). An analysis was carried out with gas chromatography Agilent 5890 B with a mass detector Agilent 5977 A. The capillary column used in this experiment was CP-WAX52CB (Agilent, 60 m × 250 μm × 0.25 μm). Helium (He) 5.0 (purity 99.999%; Messer, Austria) was used as a carrier gas. Working conditions were as follows: injector temperature at 250 °C; MSD interface temperature 250 °C; oven temperature programmed from 40 °C (2 min. hold) to 230 °C (5 min, hold) at 6 °C/min; carrier gas (He) at a flow rate of 1 mL/min. (average velocity 25.502 cm/sec); injection port operated in split less mode. The compounds were identified by comparing their mass spectra with the spectral library (Wiley 9, NIST 0.8) and expressed as peak area. Three replicate measurements were performed for each sample.