Investigation of drugs diffusion into collodion membranes using FTIR-ATR and step-scan FTIR-PAS techniques

Fourier transform infrared attenuated total reflectance (FTIR-ATR) and step-scan Fourier transform infrared photoacoustic spectroscopic (FTIR-PAS) techniques were applied to analyze penetration of dithranol and ketoconazole into artificial dodecanol-collodion (DDC) membranes. Based on Fick's second law, the problem of a drug's spatial and time dependent distribution in the membrane was solved. Dithranol diffusion results obtained by FTIR-ATR measurement were used to verify correctness of the obtained solution. Comparing experimental data with a theoretical curve allowed for determination of the diffusion coefficient of dithranol in the DDC membrane. Based on a model describing the concentration of diffusing matter, it was possible to calculate distribution of heat sources and the temperature distribution in the membrane illuminated by modulated light. A proposed mathematical model was used for interpretation of step-scan FTIR-PAS data. Using a multiparameter fitting procedure, one has determined the diffusion coefficient of ketoconazole in the DC membrane. Obtained results confirmed usability of FTIR-ATR and step-scan FTIR-PAS techniques for studies of diffusion processes.