Basic Information

Abstract Number: 2370-9     Author Name: Richard Spragg Affiliation: PerkinElmer LAS Session Title: Tools for Pharmaceutical Analysis Event Type: Poster Event Title: Comparing Raman and FTIR Spectroscopy for Characterizing Pharmaceutical Co-Crystals Presider(s):   Start Time: ( Slot # 9 ) Date: Wednesday, March 11th, 2009 Location: Keywords: FTIR, Infrared and Raman, Pharmaceutical, Raman

Co-Authors

Name Affiliation Alexander, Robert PerkinElmer LAS Borden, Farrel PerkinElmer LAS Issa, Nizar University College London

Abstract Content

Recent years have seen considerable growth in the study of co-crystals as tools to modify the solubility and stability of crystalline forms of active pharmaceutical ingredients (APIs). Co-crystals represent an interesting alternative to salts which require suitable ionization sites in the API. Their formation is generally the result of favorable hydrogen bonding interactions between the two molecules leading to a crystal with a uniform structure. They are typically prepared by evaporation of solutions containing both compounds or by grinding a slurry of the two in a poor solvent. We have compared FTIR and Raman spectroscopy as techniques for the characterization of co-crystals, both being widely used for the study of polymorphs and solvates of APIs. Although FTIR spectra generally allow different forms to be distinguished we find two potential limitations. One is that the major spectral changes are often associated with the hydrogen bonding features which are usually broad and often overlap between different forms. Another is that the appearance of the spectra may be sensitive to grinding procedures, leading to uncertainty in the origin of spectral differences. Raman spectra require no sample preparation and are generally somewhat simpler than the corresponding IR spectra. Our conclusion is that Raman spectroscopy is the technique of choice for investigating co-crystal formation.