SUPPORTED LIQUID MEMBRANES FOR ENANTIOSELECTIVE TRANSPORT OF AMINO-ACID MEDIATED BY CHIRAL CROWN-ETHER - EFFECT OF MEMBRANE SOLVENT ON TRANSPORT RATE AND MEMBRANE STABILITY

The effect of membrane solvent on transport efficiency and membrane stability was investigated in a crown ether-mediated enantioselective amino acid transport system. Relatively non-volatile organic liquids were evaluated as membrane solvents in a supported liquid membrane (SLM) using a microporous polymer film as solid support. For the organic liquids giving high fluxes and a high enantioselectivity, the membrane stability was assessed by operating the membranes for periods of up to 90 days. During these experiments, test-runs were repeated daily and thus the experiments were termed `repeated-run' experiments. The best organic liquids were found to be o-nitrophenyl octyl ether (ONPOE) and p-nitrophenyl heptyl ether (PNPHE). SLMs with these organics were stable for more than 50 repeated-runs. The factors controlling the membrane efficiency are discussed on the basis of the physico-chemical properties of the organic liquids, and it is found that the membrane solvent must have both a high dielectric constant and low solubility in water for the SLMs to be highly stable and permeable.