Separation and nucleation kinetics of l-menthol polymorph through a swift cooling crystallization process

Abstract

L-Menthol is one of the most important flavouring and additive agents found naturally in plants (mint family). In the present work, the polymorphic separation of L-menthol from saturated aqueous solution is carried out through a swift cooling crystallization process with varying relative supersaturation conditions σ = 2.36 to 7.3. Nucleation of the form-II polymorph of L-menthol is observed with varying induction times throughout the experiment and the nucleation, morphology and growth behaviour were demonstrated using optical microscopy. The nucleation kinetics of L-menthol based on classical nucleation theory was studied using the experimentally obtained induction time and relative supersaturation. Further, the internal structure and thermal stability of the grown crystal were confirmed by powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) analyses.