(579f) Discriminate the Differences Between Surface Water and Channel Water in the Formation of Solvates

Discriminate the differences between Surface water and Channel
water in the formation of solvates

Yumin Liu^1,2,
Dandan Han^1,2, Jingkang Wang^1,2, Junbo Gong^1,2*

¹ National Engineering Research
Center of Industry Crystallization Technology, School of Chemical Engineering
and Technology, Tianjin University, Tianjin, China;

² The Co-Innovation Center of
Chemistry and Chemical Engineering of Tianjin, Tianjin University, Tianjin,
China;

E-mail address: liuyumin@tju.edu.cn     junbo_gong@tju.edu.cn ^*

Abstract

Solvates
are defined as Active Pharmaceutical Ingredients (APIs) solids which
incorporate one or more solvent molecules in the crystal lattice or channel to
form new crystalline substances. Converting the drugs into hydrophilic solvates
can help to improve the solubility in water and increase drug bioavailability.
Meanwhile, it also can improve the stability of drugs, thus facilitating the
formulation and storage of the drugs. There are four binding modes between
compounds and solvents, just presented in the following Figure 1. Liquid
inclusions and incorporation into the lattice are composed of solvates. With
the increased incidence of solvate formation, it is essential to get a
comprehensive understanding of their structure, physical stability, and the
implication of de-solvation on the properties of the APIs. Hydrate are the most
abundant solvates, owing to the high propensity of water to be entrapped in the
lattice of APIs, with its small size and tendency to form multi-directional
hydrogen bonds. Pharmaceutical solids may come in contact with water during
processing steps, such as crystallization, lyophilization, spray-drying, wet
granulation, or aqueous film-coating, and they may be exposed to humid air
during storage. Absorbed water molecules may reside on crystal surfaces, in
crystal channel, or in crystal lattice structures which can change the packing
in the unit cell. Surface water and channel water is quite different from each
other. Without a doubt, we can utilize SXRPD to discriminate that differences
between them. But in our laboratory, 
 several other offline analytical
techniques, such as XRPD, TGA and DVS, were also adopted to distinguish it and
achieved remarkable results.

Fig.1 Different principles of solvent
associations with crystalline solids