Handbook of Solvents - George Wypych - ChemTech - Ventech!

1124 Christine Barthélémy, Michel Bauer
This study enables us to underline some considerations about the drying conditions of
crystals. It is important to note that not only should the usual parameters be taken into account,
such as the melting point of the substances and the boiling point of the solvents, but
also the texture of the particles and the thermodynamic events that can occur when the substance
is heated.
The kinetic of temperature increase must be chosen with respect to crystalline particle
texture to obtain optimal drying conditions for lowest RS content. Progressive drying can
give better solvent elimination when the texture is very finely sintered to avoid the crusting
effect, which hinders any ulterior solvent escape. 2
When a solvate is formed, the drying temperature must be either equal to or higher
than the desolvation temperature.
Lastly, the knowledge of the existence of solid-solid transitions could be in this respect
of great interest. Thermogravimetry and DSC analysis are, among others, very efficient
tools to assess these phenomena.
References
1 European Pharmacopoeia, 3rd edition, addendum 1999, pp. 216-224.
2 C. Barthélémy, P. Di Martino, A-M. Guyot-Hermann, Die Pharmazie, 50, 609 (1995).
3 A. Ettabia, C. Barthélémy, M. Jbilou, A-M. Guyot-Hermann, Die Pharmazie, 53, 565 (1998).
4 Y. Kawashima, M. Okumura, H. Takenaka, Science, 216, 1127 (1982).
5 J-M. Fachaux, A-M. Guyot-Hermann, J-C. Guyot, P. Conflant, M. Drache, S. Veesler, R. Boistelle,
Powder Techn., 82, 2, 123 (1995).
6 Note for Guidance on impurities: Residual solvents, Drugs made in Germany, 41, 98 (1998).
7 F. Guillaume, A-M. Guyot-Hermann, Il farmaco, 48, 473 (1993).
8 M. Jbilou, A. Ettabia, A-M. Guyot-Hermann, J-C. Guyot , Drug Dev. & Ind. Pharm., 25, 3, 297 (1999).
9 A. Ettabia, E. Joiris, A-M. Guyot-Hermann, J-C. Guyot, Pharm. Ind., 59, 625 (1997).
10 A. Ettabia, European Thesis, Lille II University, France (8/10/1997).