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Journal of Analytical Methods in Chemistry
Volume 2012, Article ID 439082, 9 pages
http://dx.doi.org/10.1155/2012/439082
Research Article

Thermoanalytical Investigation of Some Sulfone-Containing Drugs

1Pharmaceutical Chemistry Department, National Organization for Drug Control and Research, Pyramids Avenue, P.O. Box 29, Giza, Egypt
2Analytical Chemistry Department, Faculty of Pharmacy, Helwan University, Cairo 1860, Egypt
3Analytical Chemistry Department, Faculty of Pharmacy, Mansoura University, Mansoura 35516, Egypt

Received 3 November 2011; Revised 13 February 2012; Accepted 20 February 2012

Academic Editor: Pablo Richter

Copyright © 2012 Nahla N. Salama et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The thermal behavior of some sulfone-containing drugs, namely, dapsone (DDS), dimethylsulfone (MSM), and topiramate (TOP) in drug substances, and products were investigated using different thermal techniques. These include thermogravimetry (TGA), derivative thermogravimetry (DTG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). The thermogravimetric data allowed the determination of the kinetic parameters: activation energy (Ea), frequency factor (A), and reaction order (n). The thermal degradation of dapsone and topiramate was followed a first-order kinetic behavior. The calculated data evidenced a zero-order kinetic for dimethylsulfone. The relative thermal stabilities of the studied drugs have been evaluated and follow the order DDS > TOP > MSM. The purity was determined using DSC for the studied compounds, in drug substances and products. The results were in agreement with the recommended pharmacopoeia and manufacturer methods. DSC curves obtained from the tablets suggest compatibility between the drugs, excipients and/or coformulated drugs. The fragmentation pathway of dapsone with mass spectrometry was taken as example, to correlate the thermal decomposition with the resulted MS-EI. The decomposition modes were investigated, and the possible fragmentation pathways were suggested by mass spectrometry.