Introduction to the Solid State – Physical Properties and Processes

Periodic DFT Calculations—Review of Applications in the Pharmaceutical Sciences

“…For example, solid state nuclear magnetic resonance can be used as a perfect tool to study the pharmaceutical solids, both APIs and final dosage forms [25]. However, both the solid-state analysis itself as well as the interpretation of its results is in many cases much more complex than in the case of liquid state samples [26].…”

Optimizing the Quality of Food Powder Products: The Challenges of Moisture-Mediated Phase Transformations

“…The driving forces for the transition between the anhydrous and hydrate form of a crystal are the external RH (or a w ) and temperature (Vippagunta et al 2001). As temperature and a w change, the Gibbs free energies of the hydrate and anhydrous forms shift, eventually intersecting where a conversion becomes thermodynamically favorable (Ymén 2011). Van 't Hoff plots of the solubility of the anhydrate and the hydrate solids versus temperature can be used to determine the hydrate-anhydrate transition temperature, which is the point at which both forms have equal solubilities, free energies, and stabilities (Grant & Higuchi 1990).…”

“…The critical a w of the anhydrate-hydrate transition at each temperature below the critical temperature is also important but can be difficult to measure because the kinetics of hydrate formation or loss can be very slow (months to years), metastable structures can exist, and there is an activation energy required for the phase change (Franks 2013, Scholl & Schmidt 2014a. Solution-mediated approaches reduce the amount of time and potentially provide greater accuracy for identifying the critical a w s at different temperatures than water vapor-mediated approaches (water vapor sorption profiling and controlled RH desiccator storage studies) (Allan & Mauer 2017a,b;Ymén 2011;Zhu et al 1996). These approaches have enabled the creation of RH-temperature phase diagrams of deliquescent hydrate-forming crystalline ingredients that document the phase boundaries for both deliquescence and anhydrate-hydrate transitions (Allan & Mauer 2017a,b) (Figure 3).…”