Solution-mediated transformation of α to β L-glutamic acid:: Rate enhancement due to secondary nucleation

The ability to control the transformation process between polymorphs of crystalline materials is critical to ensure that the correct form is produced, and hence it is essential to learn which experimental factors affect this transformation reaction. In this contribution, the kinetics of the polymorphic transformation between metastable and stable forms Of L-glutamic acid was studied using a number of techniques: optical microscopy, FT-IR, Raman and UV spectroscopy. The effects of solution composition and in particular process scale were investigated. The role of secondary nucleation in which the surface of one polymorph acts as a template for the nucleation of another form is highlighted in this paper.