Analytical characterization of the flavor of oxygen-spoiled wines through the gas chromatography ion-trap mass spectrometry of ultratrace odorants:: Optimization of conditions

A method for the direct determination of the most important aromas generated in oxygen-spoiled wines is developed. The method allows the simultaneous determination of some key ultratrace carbonyls, such as t-2-hexenal, t-2-octenal, and t-2-nonenal; other carbonyls such as furfural, 5-methyl furfural, hexanal, and benzaldehyde; some alcohols, such as 1-octen-3-ol, 2-buthoxyethanol, and furfurol; and a volatile phenol, such as eugenol. Only one internal standard is used, and chemical derivatization of carbonyls is not required. The method combines a powerful preconcentration based on the demixture of an alcoholic fraction by salting out the wine with a liquid-liquid microextraction of an ether-pentane (10:90) mixture. The first step guarantees sensitivity, and the second step ensures selectivity and cleanliness. The extract, which is enriched between 200- and 2000-fold in the analytes, is directly injected into the gas chromatography-ion-trap mass spectrometry system. The preconcentration, injection, and mass-selective detection analysis steps have been optimized with both synthetic and real extracts in order to reach a reasonable compromise among sensitivity, selectivity, and cleanliness. The method is free from matrix effects, and linearity is satisfactory. The global method reproducibility ranges from 3 to 7% for most of the analytes. Detection limits range from 10 to 600 ng/L.