Crystallisation from water-in-oil emulsions as a route to spherical particulates: Glycine and the hydrochloride salts of glutamic acid and ephedrine

Emulsion crystallization has been reported as an approach to controlling particle properties, and is part of a wider set of techniques that can be used to form spherical particles. In the pharmaceutical industry, spherical particles are known to present distinctive advantages in terms of flow and compression properties, for example over needles or laths. This study sought to define a possible working space for the development of emulsion crystallisation of materials that could mimic pharmaceutically active compounds. Crystallisation of three water-soluble materials, glycine, L-glutamic acid hydrochloride, and ephedrine hydrochloride from water-in-oil emulsions is explored. In particular, work on these compounds shows that the combined importance of stirring and surfactant and templating additive choice is evident in developing a practical route to utilising this technology. It is also evident that the relative solubility of the solute in the two liquid phases may totally preclude the use of the drops as crystallisation environments and lead to the unwanted growth of large crystals in the continuous phase. © 2009 American Chemical Society.