Proposal of Evaluation Method for Amount of Mother Liquor in Spherical Agglomerates

Abstract

In Indomethacin crystallization, α-form crystals can be formed as spherical agglomerates by using anti-solvent crystallization in which NaCl aqueous solution is used as anti-solvent in the presence of a liquid–liquid phase separation. Since the spherical agglomerates were formed, it was considered that mother liquor is strongly affected purity of the spherical agglomerates. Therefore, new method is necessary to evaluate the amount of mother liquor in spherical agglomerates. The purpose of this present study is to propose removable factor ω which can evaluates the amount of removable mother liquor (mother liquor which is able to be removed by washing). The amount of removable mother liquor in spherical agglomerates which was obtained under the condition of different NaCl concentration and stirring speed was evaluated by using ω. From experimental results, it was found that ω decreased with the increase of NaCl concentration and the decrease of stirring speed. Furthermore, these experimental phenomena could be explained from the viewpoint of aggregate structure. So, it was confirmed that the evaluation method by using ω was reasonable. The new evaluation method could be proposed to evaluate the amount of removable mother liquor in spherical agglomerates which was obtained under the various operating conditions.