Selective photofacilitated transport of sodium ions through liquid membranes: key factors in experimental design, transport results and comparison with a mathematical model

Using photoactive carriers, the facilitated flux of solutes through liquid membranes can be controlled spatially and temporally with light. An improved understanding of this interesting yet complicated process can be achieved through a combination of mathematical modeling and experiments. In order to test the predictions of a model developed by Longin et al. [J. Phys. Chem. B 101 (1997) 7172; J. Phys. Chem. B 102 (1998) 2064; J. Phys. Chem. B 102 (1998) 1036], an experimental system was designed and related techniques were developed. Key factors in the experimental system included design and operation of a transport cell, physical properties of the carrier, membrane support and solvent, and light intensity. Results for selected facilitated transport of sodium ions through a 2-fluorotoluene liquid membrane using dicyclohexano-18-crown-6 as the carrier are reported in order to verify the adequacy of the experimental system. Selective photofacilitated transport of sodium ions was carried out using a photoactive crown ether. The flux for sodium ions under illumination was five to seven times greater than the flux in the dark. The magnitude of the photofacilitation effect is in qualitative agreement with the predictions of the model.