DETERMINATION OF HYDROXYL-GROUPS AND FREE-WATER ON SILICA-GEL IN THE NEAR-INFRARED REGION

The paper deals with the interpretation of fundamental, combination, and first overtone vibration signals of OH groups and H2O on silica gel. A signal at 4425 cm-1 is assigned to vibrations of free OH groups, while a signal at 4505 cm-1 is attributed to vibrations of the sum of all OH groups, independently of their types. A molar absorption coefficient of H2O signal at 5235 cm-1 was determined. Fundamental bands of H2O and OH groups in the 3100-3800 cm-1 range cannot be separated and interpreted quantitatively. © 1990.