Towards a better understanding of the nucleation behavior of α and γ polymorphs of glycine from aqueous solution in the presence of selective additives by charge compensation mechanism

Abstract

The type of polymorphic nucleation of glycine observed at any instant of time mainly depends on the charge environment of the experimental solution and this is discussed based on the perspective of charge compensation mechanism among the molecular species. The nucleation of α takes place due to self-charge compensation by glycine molecules whereas, γ nucleation occurs by overcoming of self-charge compensation by induced charge compensation in smaller proportions through the charged ions of the externally added induced charge compensators sodium nitrate (ICCNaNO3) and sodium hydroxide (ICCNaOH). The overcoming of self-charge compensation occurs at the critical concentration of the induced charge compensators. Nucleation behaviour of the glycine polymorphs obtained in the present work has been compared with that obtained in our previous work with sodium acetate as ICC. Influence of these ICC charged ions on the solubility, pH, supersaturation, induction time, nucleation and growth of the nucleated polymorphs were studied. Structural conformation and probability nucleation ratio of the nucleated polymorphs were confirmed by powder x-ray diffraction.