Effect of Amino Acid Additives on the Crystallization of l-Glutamic Acid

• Published in: Crystal growth & design 2005-03, Vol.5 (2), p.593-597
• Main Authors: Cashell, Caitriona, Corcoran, David, Hodnett, B. Kieran
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; General studies of phase transitions; Nucleation; Physics; Structure of solids and liquids; crystallography
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/cg049712h

The influence of a range of amino acid additives on the crystallization of l-glutamic acid has been investigated. The presence of a bulky side chain (phenyl) in l-phenylalanine and l-tyrosine was identified as an essential feature in achieving stabilization of the α-polymorph at low additive concentrations. Minute quantities of these additives were incorporated into the α-l-glutamic acid product crystals when the additive/l-glutamic molar ratio was 1:30 in solution; in this condition no β-form inclusions were observed inside the α-form crystals. At higher additive/l-glutamic acid molar ratios in solution (1:6), a significant amount of additive uptake was observed and changes in α-form morphology were noted under these conditions. A key feature was the disappearance of the {011} and {001} facets of α-l-glutamic acid and the emergence of the {111}and {110} facets. The overall hypothesis is that additives disrupt the developing β/α interface and this stabilizes the α-form.