Abstract This work reports the mechanochemical synthesis and characterization of a cocrystal formed by norfloxacin (NOR) and nicotinic acid (NCA). The thermal analysis provided the thermal stability and appropriated stoichiometry of NOR-NCA cocrystal. In addition, the crystalline structure and the coordination sites were obtained through Fourier-transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRPD). This allowed the determination of NOR-NCA interaction in the cocrystal state: the amine group of NOR interacts simultaneously with the aromatic nitrogen and the hydroxyl of the carboxyl group of NCA. Moreover, NOR-NCA crystallized in the monoclinic crystal system, space group Pa, and Z = 4, Z’ = 2. Finally, solubility assays showed an increase of NOR solubility of 2 times in pH 6.1 buffer solution. On the other hand, the cocrystal did not show a significant change in NOR solubility in pH 3.0 buffer solution, while presented a slight decrease in pH 8.5 buffer solution, which shows a pH-dependency.

中文翻译：

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诺氟沙星-烟酸共晶：机械化学合成、热和结构表征以及溶解度测定

摘要 这项工作报告了由诺氟沙星 (NOR) 和烟酸 (NCA) 形成的共晶的机械化学合成和表征。热分析提供了 NOR-NCA 共晶的热稳定性和合适的化学计量。此外，晶体结构和配位位点是通过傅里叶变换红外光谱（FTIR）和 X 射线粉末衍射（XRPD）获得的。这允许确定共晶状态下的 NOR-NCA 相互作用：NOR 的胺基团同时与 NCA 的芳族氮和羧基的羟基相互作用。此外，NOR-NCA 在单斜晶系、空间群 Pa 和 Z = 4、Z' = 2 中结晶。最后，溶解度测定显示 NOR 在 pH 6.1 缓冲溶液中的溶解度增加了 2 倍。另一方面，