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 st ability was investigated in a crown ether-mediated enantioselective am ino acid transport system. Relatively non-volatile organic liquids wer e evaluated as membrane solvents in a supported liquid membrane (SLM) using a microporous polymer film as solid support. For the organic liq uids giving high fluxes and a high enantioselectivity, the membrane st ability was assessed by operating the membranes for periods of up to 9 0 days. During these experiments, test-runs were repeated daily and th us the experiments were termed `repeated-run' experiments. The best or ganic liquids were found to be o-nitrophenyl octyl ether (ONPOE) and p -nitrophenyl heptyl ether (PNPHE). SLMs with these organics were stabl e for more than 50 repeated-runs. The factors controlling the membrane efficiency are discussed on the basis of the physico-chemical propert ies 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.