Nature of Hydrogen Bonding of Water Molecules in Aqueous Solutions of Glycerol by Attenuated Total Reflection (ATR) Infrared Spectroscopy

Attenuated total reflection infrared (ATR-IR) spectroscopy was performed on glycerol/water solutions in order to gain a better understanding of the strong hydrogen bonding of glycerol as a humectant. The OH stretching band after eliminating the contribution of glycerol OH in the glycerol/water solutions was decomposed using three Gaussian components. With increasing glycerol concentrations up to 50 volume %, the decrease of the 3428 cm⁻¹ component (middle H-bond component) and the increase of the 3562 cm⁻¹ component (longer H-bond component) suggested the breaking of H bonds among water molecules. On the other hand, the 3242 cm⁻¹ component (shorter H-bond component) remained unchanged. It was expected that water molecules surrounding glycerol molecules are retained by strong H bonding between H atoms of water and O atoms in C–O of glycerol when aqueous solutions containing glycerol are introduced in human skin.