Comparison of permeability data from traditional diffusion cells and ATR-FTIR spectroscopy .1. Synthetic membranes

Diffusion cells and attenuated total reflectance Fourier transform infra-red (ATR-FTIR) spectroscopy have been used to monitor the permeation of a model compound, 4-cyanophenol (CP), across silicone membranes. CP permeation was measured across water saturated silicone membranes and untreated silicone membranes. In all cases the donor phase consisted of a saturated aqueous solution of CP. The receptor phase used in the diffusion cells was distilled water. After calibration of the ATR-FTIR system, it was found that the water saturated membranes yielded permeability co-efficients for CP identical to those found using diffusion cells. In contrast, it was found that the permeability coefficient determined from the ATR-FTIR spectroscopy data for the untreated membrane yielded a value almost two-fold greater than those obtained from both the diffusion cells and the ATR-FTIR spectrometer with the pre-saturated membranes. It is likely that the untreated membrane used in the diffusion cell study contained a substantial amount of water before application of the donor solution due to the inevitable uptake of the water receptor medium. Therefore, as a result of the experimental techniques and procedures used, the only membrane that was not hydrated to some degree before the donor phase was applied was the untreated one analysed by ATR-FTIR spectroscopy. It has been demonstrated that, provided all initial conditions are effectively the same, there is a good correlation between permeability co-efficients measured using diffusion cells and ATR-FTIR spectroscopy. (C) 1997 Elsevier Science B.V.