**2. Materials and Methods**

#### *2.1. Materials*

Florfenicol was offered by Ruipu Bio-Pharmacy Co., Ltd. (Tianjin, China) with a mass fraction purity higher than 99.5%. The organic solvents including methanol, ethanol, 1-propanol, and isopropanol used in this work were offered by Jiangtian Chemical Co., Ltd. (Tianjin, China) and the mass fraction purities of all selected solvents are higher than 99.5%. Deionized water was supplied by Yuanli Chemical Co., Ltd. (Tianjin, China).

#### *2.2. Characterization of Florfenicol*

The crystal form of florfenicol samples was identified by Powder X-ray diffraction (PXRD, Rigaku, Japan, D/MAX 2500). The region of scanning angle was from 2 to 45◦ with a scanning rate of 5◦/min. All the X-ray diffraction measurements were carried out at room temperature and atmospheric pressure. The melting properties of florfenicol were measured using a differential scanning calorimeter (DSC, Mettler Toledo, Zurich, Switzerland). The measurement was under the protection of nitrogen at a heating rate of 2 K/min.
