Particle and powder properties of cyclodextrins

Abstract

The particle and powder properties of α-,β-,γ- and hydroxypropyl-β- (HPβ) cyclodextrins (CDs) were examined. Special attention was paid to water interaction and thermal properties of CDs. The CDs studied showed big differences in particle size distribution and particle shape. In all cases, with the exception of βCD, the log-normal distribution described adequately the particle size distribution. However, the beta-distribution characterized well particle shape factor distribution. The typical α and β parameters obtained from the beta-distribution fitting are related to sphericity and shape uniformity of the particles. Water content results for CDs, obtained by loss on drying at 160°C and Karl Fisher methods, yielded similar results; thus, it was possible to evaporate practically all the water at 160°C. Water content of CDs ‘as received’ was dependent on the storage history of the samples after manufacturing. The DSC profiles of the CDs showed a broad, intense endothermic effect in the range 20–130°C, this asymmetric peak was ascribed to water removal. αCD showed a characteristic peak with an onset temperature 138°C. This peak seems to be independent of water content, and only small modifications are observed after drying at high temperature. Thus, a feasible structural change is associated with this peak.