title: Combined synchrotron XRD/Raman measurements: in situ identification of polymorphic transitions during crystallization processes.
abstract: A combination of two analytical methods, time-resolved X-ray diffraction (XRD) and Raman spectroscopy, is presented as a novel tool for crystallization studies. An acoustic levitator was employed as sample environment. This setup enables the acquisition of XRD and Raman data in situ simultaneously within a 20 s period and hence permits investigation of polymorphic phase transitions during the crystallization process in different solvents (methanol, ethanol, acetone, dichloromethane, acetonitrile). These real time measurements allow the determination of the phase content from the onset of the first crystalline molecular assemblies to the stable system. To evaluate the capability of this approach, the setup was applied to elucidate the crystallization process of the polymorphic compound nifedipine. The results indicate the existence of solvent-dependent transient phases during the crystallization process. The quality of the data allowed the assignment of the lattice constants of the hitherto unknown crystal structure of the beta-polymorph.
authors.affiliation: BAM Federal Institute for Materials Research and Testing, Richard-Willstaetter-Str. 11, D-12489 Berlin, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Klimakow
authors.forename: Jork
authors.initials: J
authors.lastname: Leiterer
authors.forename: Janina
authors.initials: J
authors.lastname: Kneipp
authors.forename: Ernst
authors.initials: E
authors.lastname: Rössler
authors.forename: Ulrich
authors.initials: U
authors.lastname: Panne
authors.forename: Klaus
authors.initials: K
authors.lastname: Rademann
authors.forename: Franziska
authors.initials: F
authors.lastname: Emmerling
mesh_terms: D003460:Crystallization; D008962:Models, Theoretical; D015394:Molecular Structure; D013059:Spectrum Analysis, Raman; D017356:Synchrotrons; D014961:X-Ray Diffraction