Headspace solid-phase microextraction method for determining 3-alkyl-2-methoxypyrazines in musts by means of polydimethylsiloxane-divinylbenzene fibres

A method for determining 2-methoxypyrazine, 3-methyl-, 3-ethyl-, 3-isopropy l-, 3-sec.-butyl- and 3-isobutyl-2-methoxypyrazine in musts is described. I t involves headspace solid-phase microextraction (SPME) and determination b y capillary gas chromatography using nitrogen-phosphorous detection. Pyrazi nes were satisfactorily separated under isothermal conditions, and quantifi cation was carried out using 3-isopropyl-2-ethoxypyrazine as the internal s tandard. Ionic strength, time and temperature were studied in order to make SPME as efficient as possible. The developed method enabled detection limi ts at the 0.1 ng l(-1) levels for some of the analytes. The method was succ essfully applied to identify and quantify different 3-alkyl-2-methoxypyrazi nes in experimental musts of Cabernet Sauvignon and Merlot. Their evolution during the ripening was also monitored. (C) 2000 Elsevier Science B.V. All rights reserved.