Polymorph Control of L‐Phenylalanine in Cooling Crystallization by Ultrasonication

Most of the amino acids that are utilized as medical raw materials and food additives show polymorphism. To improve the physical and chemical properties of the crystals, an effective method for polymorph control is required in the crystallization process. In this study, polymorph control of L‐phenylalanine in cooling crystallization by ultrasonication was investigated. L‐Phenylalanine crystallizes in anhydrate and monohydrate forms. Without ultrasonication, a mixture of monohydrate and anhydrate forms was obtained. In contrast, the yield of monohydrate was increased by ultrasonication. In addition, ultrasonication shortened the induction time. It was considered that ultrasonic energy could supply the energy required for primary nucleation. Amino acids are utilized as medical raw materials and food additives. Most amino acids show polymorphism, and polymorph control is required in the crystallization process. In this study, polymorph control of L‐phenylalanine monohydrate was achieved by ultrasonication. The effect of ultrasonication on primary nucleation can be estimated from the energy required to form a critical nucleus.