Ehiwe, Tracy O., Alexander, Bruce D., Mitchell, John C., Snowden, Martin J and Waters, Laura J. (2016) Monitoring real time polymorphic transformation of sulfanilamide by diffuse reflectance visible spectroscopy. Journal of Pharmaceutical Analysis, 6 (3). pp. 179-183. ISSN 2095-1779

This study investigated the development of a novel approach to surface characterisation of drug polymorphism and the extension of the capabilities of this method to perform ‘real time’ in situ measurements. This was achieved using diffuse reflectance visible spectroscopy (DRV spectroscopy) and dye deposition, using the pH sensitive dye, thymol blue (TB). Two polymorphs, SFN-β and SFN-γ, of the drug substance sulfanilamide (SFN) were examined. The interaction of adsorbed dye with polymorphs showed different behavior, and thus reported different DRV spectra. Consideration of the acid/base properties of the morphological forms of the drug molecule provided a rationalization of the mechanism of differential coloration by indicator dyes. The kinetics of the polymorphic transformation of sulfanilamide polymorphs was monitored using treatment with TB dye and DRV spectroscopy. The thermally-induced transformation fitted a first-order solid-state kinetic model (R2 = 0.992), giving a rate constant of 2.43 x 10−2 s−1.

Accepted manuscript
1-s2.0-S2095177915300198-main.pdf__tid=716011f2-b600-11e5-9ce5-00000aacb35d&acdnat=1452255052_a2be0b8802a1f486175ba26d82e1a5d1 - Published Version
Available under License Creative Commons Attribution Non-commercial No Derivatives.

Download (833kB)


Downloads per month over past year

Add to AnyAdd to TwitterAdd to FacebookAdd to LinkedinAdd to PinterestAdd to Email