Water and temperature induced polymorphic transformations of mannitol

The effects of water and temperature on the polymorphic transition of crystalline mannitol were investigated. Mannitol has different polymorphic forms, and was classified as alpha, beta, and delta form, respectively, by Walter-Le´vy (C.R. Acad. Sc. Paris Ser. C (1968) 267, 1779). The behavior of representative crystalline form was studied using water granulation and temperature induced mechanism. The different powder X-ray diffraction patterns obtained before and after water granulation confirmed that water induced polymorphic transition had occurred. Morphological changes were observed with increase in the specific surface area of the sample from 1.044 to 1.206m2/g, It was also found that decrease the particle size upon water granulation. At the same time temperature induced polymorphic transformation observed using Differential Scanning Calorimetry (DSC), were reported glass transition temperature of Mannitol is determined from inferences. The glass transition temperature denotes the stability of amorphous Mannitol, which is necessary to be stored only below this grass transition temperature else it may easily re-crystallize in to a thermodynamically stable crystalline form. When considering the mechanism of these polymorphic transitions, the results from PXRD, DSC, TGA, BET SSA, PSD and Sorption analysis indicates that water granulation process leads to the polymorphic transformation and increases the specific surface area with decrease in particle size initially, but later it gets agglomerated over a period of time resulting increase in particle size . Where as temperature induces polymorphic transformation from crystalline to amorphous, which needs to be stored below its glass transition temperature.