Gas chromatographic amino acid profiling of wine samples for pattern recognition

A rapid gas chromatographic profiling and screening method is described for the determination of free amino acids in wine samples. The amino acids in alkaline aqueous wines were allowed to react with isobutyl chloroformate. The resulting N(O,S)-isobutyloxycarbonyl amino acids were extracted by solid-phase extraction using Chromosorb P as the adsorbent and diethyl ether as the eluent after acidification, and then converted into stable tert.-butyldimethylsilyl derivatives with subsequent analysis by dual-capillary column gas chromatography and gas chromatography-mass spectrometry. Seventeen free amino acids were identified from the four wine brands studied. When the GC profiles were simplified to the corresponding amino acid retention index spectra in bar graphical form, they presented characteristic patterns for each wine brand. Stepwise discriminant analysis performed on the amino acid profiles provided star symbols characteristic of the wine brands.