Gas-chromatography/mass-spectrometry analysis of human skin constituents as heptafluorobutyrate derivatives with special reference to long-chain bases

The composition of the constituents (monosaccharides, long-chain bases, and fatty acids) found in an ethanol extract of the human skin could be determined, without time-consuming steps of purification, after acid-catalyzed anhydrous methanolysis, followed by the formation of volatile derivatives with heptafluorobutyric anhydride and gas-chromatography/mass-spectrometry analysis. Despite the extreme heterogeneity of such extracts, the electron impact analysis of the constituents allowed qualitative and quantitative determinations of monosaccharides, long-chain bases, fatty acids, and alkyl-glycerols. Throughout the different long-chain bases, sphingenines (Sphes), sphinganines, phytosphingosines, and 6-hydroxy-Sphes (6oh-Sphes) can be identified and quantified. Long-chain bases with a chain-length up to 28 carbon atoms can be identified through specific fragmentation patterns in the electron impact mode. Particular attention was drawn to the behavior of compounds of the family of 6oh-Sphes upon acid-catalyzed methanolysis.