Analytical Estimation of Water Contents, Specific Heat Capacity and Thermal Profiles Associated with Enzymatic Model Compound β-Cyclodextrin

Studies of water contents of solid β-cyclodextrin (β-CD) in crystallized and vacuum dried conditions are reported. Water contents were estimated using Karl–Fischer (KF) titration and thermo-gravimetric analysis (TGA) techniques. It was found that the water contents for crystallized and vacuum-dried samples were 6.93 and 0.86 moles of water per β-CD molecule respectively. TGA studies gave values of 6.83 and 0.52 moles of water per β-CD molecule respectively. The results agree with those reported from X-ray diffraction studies. Also, the molecular weight of the vacuum dried sample was determined using vapour pressure osmometry, which agrees well with the actual molecular weight of β-CD. The thermal profiles of α-cyclodextrin (α-CD) and β-CD are presented. The differential scanning calorimetry data was used to calculate specific heat at constant pressure (C_p) at different temperatures (338.15–468.15 K). These results are compared with similar data for α-CD and discussed in terms of motional contribution to C_p values and related conformational effects.