THE INFLUENCE OF VEHICLE ON PERMEATION FROM SATURATED SOLUTIONS

The penetration of two compounds from three different vehicles through a silicone membrane has been studied. The permeants under investigation were cyanophenol and cyanonaphthalene and the solvents studied were water, ethanol and polyethylene glycol 400 (PEG 400). Initially, Franz cell experiments were conducted to determine gross vehicular and receptor phase effects. Subsequently, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy permitted the measurement of both solvent and solute permeability and the deconvolution of the diffusional and partitioning steps involved in the permeation process. It has been shown that the extent to which a vehicle may alter the degree of penetration of a substance can, in the cases studied, be related to the degree of penetration of the vehicle itself. Further, the permeant parameter that is most affected by such vehicular penetration is its solubility in the membrane under study rather than its diffusion coefficient. In situations where the permeant is at very high concentrations in the vehicle (in this case around 50% w/v) the nature of the primary permeant may start to affect the degree of penetration of the vehicle itself.