Control of Crystal Aspect Ratio and Size by Changing Solvent Composition in Oiling Out Crystallization of an Active Pharmaceutical Ingredient

Oiling out crystallization of an active pharmaceutical ingredient, API-T, was carried out under agitation using a mixed solvent (acetone/water) system, and the effects of oiling out (liquid [oily droplet phase]/liquid [continuous phase] separation) on the aspect ratio and size of crystals were investigated. Acetone composition of the oil phase and API-T distribution to the oil phase increased with a decrease in charged acetone composition, and both decreased in the continuous phase. By utilizing this relationship, API-T crystals with small aspect ratios were produced under a low charged composition of acetone, at which a high recovery of product crystals could be expected. Furthermore, large crystals were obtained in the oiling-out crystallization. Such performance was never achieved in normal single-phase crystallization, and thus an advantage of oiling out crystallization was shown.