Growth and Dissolution Kinetics of A and B Polymorphs of L‐Histidine

Abstract

The growth rate of the stable polymorph A and the dissolution rate of the unstable polymorph B of L-histidine (L-his) in aqueous solution were experimentally determined at varying temperatures. The growth and dissolution kinetics were measured by means of desupersaturation and deundersaturation techniques, respectively. Both the growth and dissolution rates increase with higher temperature. At all temperatures studied, the dissolution rate of form B is faster than the growth rate of form A, indicating that the solution-mediated transformation of the polymorphs of L-his is likely to be controlled by the growth rate of form A. Both kinetics of the polymorphs of L-his will be used to characterize the polymorphic transformations and the overall crystallization rate of L-his.

Influence of Solvents on Solution‐Mediated Polymorphic Transformation of the Polymorphs of L‐Histidine

“…The obtained photomicrographs of the prepared crystals of forms A and B indicated that the crystals of form A exhibited rod‐like shapes consistent with those reported in previous works , , . The shape of crystals of form B appeared plate‐like like those reported in former works , , .…”

“…Pure crystals of form A of L ‐his were produced from aqueous solution crystallization by cooling operation at 25 °C as described in previous works , , , . A saturated aqueous solution of L ‐his at 45 °C was prepared at 50 °C and then the solution was cooled rapidly to 10 °C.…”

“…In literature, L ‐his is known to crystallize in a metastable polymorph B and a stable polymorph A , , . Kitamura et al , studied the formation and transformation of polymorphs of L ‐his by rapidly cooling aqueous and ethanol‐water solutions.…”

Determination of Nucleation and Growth Mechanisms of the B Polymorph of L‐Histidine by Induction Time Measurement

“…Because the B polymorph of L-his is a plate crystal [5], a 2D growth (m = 2) can be assumed. Because the growth of the L-his crystal is controlled by surface integration process [18], b = 1. For the polynuclear nucleation mechanism, the pre-exponential factor in Eq.…”

Antisolvent Crystallization of Polymorphs of L‐Histidine

“…The solubility data for water‐acetone, water‐ethanol, and water‐propanol have been reported . The data include the solubility as a function of temperature because the solubility of L ‐his increases with temperature . There are reports of the dissolution rate of form B and the growth rate of form A of L ‐his in aqueous solution , and the nucleation and growth mechanisms of form B of L ‐his in the water‐ethanol system .…”