Related Experiment Video
Updated: Jul 11, 2026

Preparation of N-(2-alkoxyvinyl)sulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines
Published on: January 3, 2018
Stable-form screening: overcoming trace impurities that inhibit solution-mediated phase transformation to the stable
Yuchuan Gong1, Benjamin M Collman, Shawn M Mehrens
1Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Weaver-Densford Hall, 308 Harvard Street S.E., Minneapolis, Minnesota 55455-0343, USA. yuchuangong@gmail.com
Abstract:
Solution-mediated phase transformation (SMPT) has been used as a focused technique to rapidly identify the stable polymorph of a given substance. Despite ample precedence for acetonitrile being a good solvent for SMPT of sulfamerazine (SMZ), samples from specific lots of SMZ failed to convert from Form I to Form II after suspension for 2 weeks in acetonitrile. In these lots, an acetyl derivative of SMZ was identified and shown to impede transformation to the stable polymorph. The inhibitory effect of this impurity on polymorphic conversion was overcome with practical adjustments to experimental procedure, which hastened the kinetics of SMPT. The critical factors considered were (1) modifying the solvent to increase solubility, (2) minimizing the level of impurity in the slurries, (3) pre-treatment of the solid to quickly reach maximum supersaturation, and (4) temperatures that optimized kinetics as well as the free energy difference between enantiotropically related polymorphs.
Related Concept Videos
Factors Affecting Dissolution: Polymorphism, Amorphism and Pseudopolymorphism
Some polymorphic crystals possess lower aqueous solubility than their amorphous counterparts, leading to incomplete absorption. For instance, the oral suspension of Chloramphenicol, which...
Phase II Reactions: Sulfation and Conjugation with α-Amino Acids
Pharmaceutical Alternatives: Polymorphic Form-Related and Particle Size-Related Therapeutic Nonequivalence
Colloidal precipitates
Antiprotozoal Agents
Washing, Drying, and Ignition of Precipitates
