Determination of odour-causing volatile organic compounds in cork stoppers by multiple headspace solid-phase microextraction

Multiple headspace solid-phase microextraction (MHS-SPME) coupled with gas chromatography-mass spectrometry has been applied in order to determine 2,4,6-trichloroanisole (2,4,6-TCA), guaiacol, 1-octen-3-ol and 1-octen-3-one in three samples of cork stoppers. These compounds are responsible for cork taint in wine and can modify the organoleptic properties of bottled wine. Variables such as temperature, addition of water, extraction time, and amount of cork were studied. The extractions were performed with a 50/30 μm divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS) fibre for 45 min at 100 °C using 20 mg of cork. For calibration, 50 μL of VOC aqueous solutions were used and the extraction were carried out for 45 min at 75 °C. The limits of detection of the method expressed as ng of VOC per g of cork were 0.3 for 2,4,6-TCA, 7.5 for guaiacol, 1.7 for 1-octen-3-one and 1.9 for 1-octen-3-ol. Relative standard deviation of replicate samples was less than 10%. Significant losses of analytes were observed when the samples were ground at room temperature. Finally, a recovery study was performed and the MHS-SPME results were validated using Soxhlet extraction results.