摘要
Studies of water contents of solid beta-cyclodextrin (beta-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 beta-CD molecule respectively. TGA studies gave values of 6.8 and 0.52 moles of water per beta-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 beta-CD. The thermal profiles of alpha-cyclodextrin (alpha-CD) and beta-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 alpha-CD and discussed in terms of motional contribution to C-p values and related conformational effects.
- 出版日期2018-6-25