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Robust bulk preparation and characterization of sulfamethazine and saccharine salt and cocrystal polymorphs

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Abstract

The complex between sulfamethazine and saccharine (SMT–SAC) can exist in two polymorphs, one is a cocrystal and the other is a salt. It is important to fully characterize the two polymorphs for a better understanding of the rare polymorphism between a salt and a cocrystal. However, this effort was hindered by the difficulty in reproducibly preparing a large quantity of phase pure cocrystal polymorph (form II). Here, we developed a method for preparing phase pure cocrystal polymorph robustly by controlling the crystallization medium. Using bulk powders, we determined their free energy diagram, by using intrinsic dissolution rates at 5–37 °C and thermal data near melting temperature. We have shown that the two forms are monotropically related, with the cocrystal form II being more thermodynamically stable up to the melting temperature. We further probed their ionization states based on analyses of the position of protons, bond length, and molecular vibrational motions of pertinent functional groups. Finally, the cocrystal form II exhibited notable differences in moisture sorption and compaction properties, which may influence the choice of solid forms for further development of tablet products.

Graphical abstract: Robust bulk preparation and characterization of sulfamethazine and saccharine salt and cocrystal polymorphs

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Publication details

The article was received on 01 Jul 2018, accepted on 13 Aug 2018 and first published on 13 Aug 2018


Article type: Paper
DOI: 10.1039/C8CE01076E
Citation: CrystEngComm, 2018, Advance Article
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    Robust bulk preparation and characterization of sulfamethazine and saccharine salt and cocrystal polymorphs

    S. R. Perumalla, C. Wang, Y. Guo, L. Shi and C. C. Sun, CrystEngComm, 2018, Advance Article , DOI: 10.1039/C8CE01076E

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