Recrystallization selectivity of amorphous lincomycin hydrochloride

The tendency of selective recrystallization of amorphous phases is highly related to its short-range order, which can be used for explaining some interesting phenomena. Amorphous lincomycin hydrochloride (ALH) with a relatively low water content tends to recrystallize into metastable sesquihydrate (Form I) instead of stable monohydrate (Form II). The IR difference spectra (IRDS) and mid-frequency Raman difference spectra (MFRDS) analysis results show that the short-range order of Form I is more similar to ALH than Form II, which explains the selective recrystallization process of ALH from structure analysis. Karl Fischer moisture titration indicates that the selective recrystallization of ALH likely follows a two-step process via hydration layers, which explains the selective recrystallization of ALH from the experimental perspective. This study on the recrystallization selectivity of ALH can provide insights into the roles that short-range order and water play in the recrystallization and storage of amorphous phases. It is necessary not only to avoid thermodynamic but also kinetic crystal phase transformation in the storage of amorphous phases. The control of storage temperature and humidity is of great significance.