Related Experiment Video
Updated: Feb 16, 2026

Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand
Published on: September 8, 2016
Mutual Impact of Phase Separation/Crystallization and Water Sorption in Amorphous Solid Dispersions
Christian Luebbert1, Maximilian Wessner1, Gabriele Sadowski1
1Department of Biochemical and Chemical Engineering, Laboratory of Thermodynamics, TU Dortmund University , Emil-Figge-Straße 70, D-44227 Dortmund, Germany.
Predicting water sorption in amorphous solid dispersions (ASDs) is crucial for stability. This study shows that crystallization and phase separation influence water uptake, and this behavior can be quantitatively predicted using PC-SAFT modeling.
Area of Science:
- Pharmaceutical Science
- Materials Science
- Physical Chemistry
Background:
- Amorphous solid dispersions (ASDs) enhance solubility of poorly water-soluble drugs.
- ASDs require stability testing under various humidity and temperature conditions.
- Previous work established thermodynamic modeling for predicting ASD stability against crystallization and phase separation.
Purpose of the Study:
- To predict water sorption in ASDs, considering API crystallization and moisture-induced amorphous-amorphous phase separation (MIAPS).
- To validate predictions with experimental data and demonstrate the interplay between water sorption and phase behavior.
Main Methods:
- Utilized perturbed-chain statistical-associating fluid theory (PC-SAFT) for thermodynamic modeling.
- Investigated ASDs of felodipine and ibuprofen with poly(vinylpyrrolidone), poly(vinyl acetate), and poly(vinylpyrrolidone-co-vinyl acetate).
- Conducted two-year water sorption experiments for validation at 25 °C/60% RH and 40 °C/75% RH.
Main Results:
- PC-SAFT successfully predicted water sorption behavior in ASDs.
- Demonstrated a significant mutual influence between API crystallization, MIAPS, and water sorption.
- Validated predictions quantitatively against long-term experimental data.
Conclusions:
- PC-SAFT is a valuable tool for predicting water sorption and phase behavior in ASDs.
- Accurate prediction of these interactions aids in early-stage formulation development.
- Understanding water sorption is critical for ensuring the long-term stability of pharmaceutical formulations.
Related Concept Videos
Structures of Solids
States of Water
Water freezes when the intermolecular forces are greater than the kinetic energy. Unlike most other substances, water is less dense in its solid state than in its liquid state. This is because each water molecule can form...
Phase Diagrams
Mutual Inductance
When two circuits carrying time-varying currents are close to one another, the magnetic flux through each circuit varies because of the changing current in the other circuit. Consequently, an emf is induced in each circuit by the changing current in the other. Therefore, this type of emf is called...
Phase Transitions: Sublimation and Deposition
Ionic Crystal Structures
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...

