title: Molecular mobility as a predictor of the water sorption by annealed amorphous trehalose.
abstract: OBJECTIVE
  The work aims at investigating the correlation of water sorption potential with different measures of molecular mobility in an annealed amorphous model compound (trehalose).
  
  
  METHODS
  Amorphous trehalose, prepared by freeze-drying, was annealed at 100°C (17°C < T                   (g)) for up to 120 h. Global molecular mobility was studied using a broadband dielectric spectrometer in the frequency range of 10(6)-10(-2) Hz. Enthalpic recovery was measured by differential scanning calorimetry and water sorption profiles were obtained using an automated vapor sorption balance.
  
  
  RESULTS
  As a function of annealing time, there was an increase, both in average α-relaxation time and enthalpic recovery and a decrease in the amount of sorbed water. A strong linear correlation was observed between the water sorption potential and the dielectric relaxation time, indicating a common underlying mechanism of the effect of annealing time on these properties. Enthalpic recovery, which is widely used as a measure of structural relaxation, did not correlate well with the extent of water sorption.
  
  
  CONCLUSIONS
  The α-relaxation time can be used as a predictor of the water sorption potential of amorphous trehalose. It will be of interest and value to develop such predictive models for other amorphous compounds of pharmaceutical interest.
authors.affiliation: Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota, 55455, USA.
authors.forename: Sunny P
authors.initials: SP
authors.lastname: Bhardwaj
authors.forename: Raj
authors.initials: R
authors.lastname: Suryanarayanan
mesh_terms: D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D058266:Dielectric Spectroscopy; D005612:Freeze Drying; D006358:Hot Temperature; D013816:Thermodynamics; D014199:Trehalose / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D014199:Trehalose