Carstensen J T, Van Scoik K
School of Pharmacy, University of Wisconsin, Madison 53706.
Pharm Res. 1990 Dec;7(12):1278-81. doi: 10.1023/a:1015942022789.
The transformation of amorphous sugar in the form of lyophilized spheres into crystalline sucrose was studied. The lyophilisate, when exposed to moist atmospheres, picks up moisture to a constant weight. The amount of moisture addition is a function of relative humidity of the atmosphere and temperature. The loose "lyophilisate structure" collapses to form a denser amorphous phase ("hydrated amorphate"). After a lag time which varies with relative humidity of the atmosphere and temperature, the hydrated amorphate loses moisture (weight) and, in the process, forms crystalline sucrose. The phase nature of the hydrated amorphate is equivalent to an aqueous solution that is supersaturated with respect to crystalline sucrose. A model was developed for the lag time which accounts for the experimental results.
