On-line HPLC photodiode array detection and OPA derivatization for partial identification of small peptides from white wine

This paper reports the possibilities of on-line reversed-phase HPLC with photodiode array detection (PDAD) and derivatization with o-phthaldialdehyde (OPA) far identification of small peptides. The methodology was initially applied to a wide range of standard peptides. Spectral parameters (wavelengths of the spectrum maxima, convexity interval, and wavelengths of the second-derivative spectrum maxima) obtained by PDAD allow identification of the aromatic amino acid residues (tyrosine, tryptophan, and phenylalanine) contained in the peptides as well as identification of other compounds from wine that can coelute with peptides (i.e. phenolic compounds). Postcolumn OPA derivatization allows confirmation of the peptidic nature of chromatographic peaks. The methodology has been successfully applied to peptide fractions (<700 Da) from eavas (Spanish sparkling wines). Peptides not containing aromatic amino acids and peptides containing only phenylalanine, tryptophan, or tyrosine as aromatic amino acids, as well as two coeluted cinnamic derivatives, were detected. To the authors' knowledge, these are the most detailed data reported to date about the composition of individual peptides from wine.