Visualisation of the heterogeneous water sorption in a pharmaceutical formulation under controlled humidity via FT-IR imaging

Opportunities exist to study sorption of water vapour into the domains of different components in heterogeneous polymeric materials via FT-IR spectroscopic imaging. This information is needed to understand the behaviour of pharmaceutical formulations under different humidity. Sorption of water in a polyethylene glycol (PEG) - griseofulvin mixture subjected to a range of relative humidity (RH) from 0.5 to 90% at a temperature of 25 degreesC has been studied via FT-IR imaging in situ using a controlled humidity transmission cell. This approach offers visualisation of the water sorption in different domains of the sample (polymer and drug). The FT-IR imaging data have shown that water sorption occurs preferentially in the domains of PEG rather than in the domains of griseofulvin. Significant increase of water sorption has been observed at a RH above 70%. The spatial distribution of the drug in the polymer did not change in the studied sample in the range of RH from 0.5 to 90%. (C) 2003 Elsevier B.V. All rights reserved.