Analysis for wine C5–C8 aldehydes through the determination of their O-(2,3,4,5,6pentafluorobenzyl)oximes formed directly in the solid phase extraction cartridge

A method for the determination of wine carbonyl compounds with 5–8 carbon atoms including 3-methylbutanal, E-2-hexenal, E-2-heptenal, E-2-octenal and phenylacetaldehyde has been developed. Aldehydes are retained in a solid phase extraction cartridge and derivatization with O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine takes place in the same cartridge at room temperature (25 °C) in 15 min. The corresponding oximes are further eluted and determined by gas chromatography–mass spectrometry. Isolation, derivatization and elution conditions were examined. Recoveries from red wines are all >94%, and are consistent from wine to wine. For white wines, recoveries for E-2-heptenal, E-2-octenal and phenylacetaldehyde are 80–85%, but are consistent from wine to wine. Precision (measured as relative standard deviation) is <7% in all cases. Method detection limits ranged from 0.12 to 0.70 (mu)g L^-1 and linearity holds at least up to 60 (mu)g L^-1 with r^2 in the range 0.9957–0.9997. The method has been applied to the determination of these components in several wine samples. Results show that phenylacetaldehyde, E-2-octenal and 3-methylbutanal can be found at concentrations above their corresponding odor thresholds in normal wines.