Infrared Spectroscopic Analysis of Disaccharides in Aqueous Solutions

Abstract

We studied infrared spectral characteristics derived from disaccharides and the interaction between disaccharides and water. Six kinds of sugar-H₂O solutions (trehalose, kojibiose, nigerose, maltose, isomaltose and sucrose) and three kinds of sugar-D₂O solutions (trehalose, maltose and sucrose) were prepared. Their infrared spectra were collected by use of a FT-IR/ATR method. The different spectral pattern in the fingerprint region was found for each sugar in H₂O solution. Especially, characteristic spectral features were observed for trehalose. We compared the absorption bands of the trehalose, maltose and sucrose spectra in H₂O with those in D₂O based on the absorption intensity and wavenumber. As the results, the solvent affected the absorption intensity rather than wavenumber shift, which was caused by the interaction between disaccharides and solvents. In addition, when plotted against the disaccharide concentration, the absorbance of glycosidic linkage and C-OH vibration bands in H₂O and D₂O, showed good linearity in trehalose, while non-linearity in sucrose. Their bands of trehalose shifted slightly both in the H₂O and D₂O and the shifts of sucrose were significant. Judging from the spectral patterns, trehalose seems to be stable in both H₂O and D₂O.