Investigation of Glycine Polymorphic Transformation by In Situ ATR-FTIR and FT-Raman Spectroscopy

The solution-mediated phase transformation of alpha-form to gamma-form glycine, including dissolution of metastable alpha-form, nucleation, and growth of stable gamma-form during polymorphic transformation, was investigated using in situ attenuated total-reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and Fourier transform Raman spectroscopy (FT-Raman). The mechanistic influence of operating parameters such as agitation speed, crystallization temperature, alpha-form seed concentration, and NaCl concentration on polymorphic phase transformation was examined. When the agitation speed, crystallization temperature, and NaCl concentration were increased, the polymorphic transformation process was improved due to the promotion of nucleation and growth of stable gamma-form, in addition to the promotion of dissolution of metastable alpha-form. Moreover, the time to induce gamma-form nucleation and complete conversion of alpha-form to gamma-form was also reduced with increasing alpha-form seed concentration.

Automated summary

The solution-mediated phase transformation of alpha-form to gamma-form glycine was investigated using in situ ATR-FTIR and FT-Raman techniques. It was found that the polymorphic transformation process could be improved by increasing the agitation speed, crystallization temperature, and NaCl concentration, which promoted the nucleation and growth of stable gamma-form as well as the dissolution of metastable alpha-form. Additionally, increasing the alpha-form seed concentration reduced the time required for gamma-form nucleation and complete conversion of alpha-form.