Quantitative analysis of saccharides by X-ray photoelectron spectroscopy

A series of saccharides, including several monohydrates and one amorphous phase, has been investigated by XPS, providing the first database of survey and high-resolution spectra for this class of compounds. Known stoichiometries and XPS-determined elemental compositions agree well. XPS has sufficient precision for distinguishing the stoichiometries of mono-, di-, and polysaccharides. The C 1s chemical shifts of the acetal and alcohol groups are similar for all samples, albeit with slight binding energy increases in the series from mono- to di- and polysaccharides. Increasing X-ray exposure causes a radiation-induced increase of the aliphatic hydrocarbon emission at 285 eV, concomitant with the appearance of a high binding energy C 1s emission peak at 289.1 eV and a decrease in the O 1s/C 1s emission intensity ratio. Formation of aliphatic hydrocarbon groups is proposed to arise from dehydroxylation, while the increase in the 289.1 eV peak can be attributed to double dehydroxylation at the C, position or partial oxidation of an alcohol or acetal group. The rate of radiation damage correlates with previously reported rates of thermally induced caramelization. Copyright (C) 2009 John Wiley & Sons, Ltd.