Model wine was prepared with (+)-tartaric acid (6 g L−1) supplied by Synth (São Paulo, Brazil)
and 10% of ethanol in MilliQ deionised water. Twenty-two standard compounds were purchased from Aldrich (Steinheim, Germany) and individual stock solutions of each component were prepared in double distilled ethanol purchased from Nuclear (São Paulo, Brazil). The final concentrations of each one of the 22 standard compounds in the model wine solution are listed between parentheses, as follows: ethyl acetate, ethyl butanoate, ethyl hexanoate, ethyl decanoate, diethyl succinate and propanol (1000 μg/L of each standard compound), ethyl propanoate, buy Veliparib ethyl 2-methylpropanoate, ethyl lactate, ethyl octanoate, ethyl 3-hydroxybutanoate, hexanol, isoamyl acetate, terpinen-4-ol and eugenol (100 μg/L of each standard compound); ethyl 2-methylbutanoate and 2-phenylethyl acetate (50 μg/L of each standard compound); 2-phenylethanol, hexanoic acid, octanoic acid, decanoic acid and dodecanoic acid (5000 μg/L of each standard compound). The pH was adjusted to 3.5 with sodium hydroxide (Nuclear, São Paulo, Brazil). Ultra-pure water was prepared using a Milli-Q water purification system (Millipore, Bedford, MA). The SPME fibre (50/30 divinylbenzene/Carboxen/polydimethylsiloxane
(DVB/CAR/PDMS) StableFlex) was BCKDHB purchased from Supelco (Bellefonte, PA). The fibre was conditioned according to the manufacturer’s recommendation prior to its first use. Sodium chloride (NaCl) of analytical grade was purchased from Nuclear Selleck Bortezomib and was oven dried at 110 °C overnight before use. Twenty microlitre headspace vials with magnetic screw caps sealed with silicone septa were purchased from Supelco. A CTC CombiPAL autosampler (CTC Analytics, Zwingen, Switzerland) with an agitator and SPME fibre was used to extract the volatiles from the sample vial headspace. The GC × GC system consisted of an Agilent 6890N (Agilent Technologies, Santa Clara, CA) equipped with a Pegasus
IV time-of-flight mass spectrometer (Leco Corporation, St. Joseph, MI). A DB-Wax column (100% polyethylene glycol; 30 m × 0.25 mm × 0.25 μm, J&W Scientific Inc., Folsom, CA) was used as first-dimension (1D) column, and a DB-17 ms column (50% phenyl-50% methylpolysiloxane; 1.70 m × 0.18 mm × 0.18 μm, J&W Scientific Inc.) was used as a second-dimension (2D) column. The GC system was equipped with a secondary column oven and non-moving quadjet dual-stage thermal modulator. During modulation, cold pulses were generated using dry nitrogen gas cooled by liquid nitrogen (Linde, Canoas, RS, Brazil), whereas heated dry air was used for hot pulses. The injector, transfer line and ion source temperature were at 250 °C.