LIQUID MEMBRANE-TRANSPORT OF AMINO-ACIDS MEDIATED BY REVERSE MICELLES

The potentialities of reverse micelles of AOT (bis(2-ethylhexyl) sodiu m sulfosuccinate) for the selective transport of tryptophane (Trp) and p-iodophenylalanine (pIPhe) are investigated using two different expe rimental devices. Winsor II systems were obtained from mixtures of AOT /isooctane/water (0.1 M phosphate buffer). The microemulsion phase was used as a liquid membrane in which the reverse micelles play the ?art of mobile carriers. In the first device there was a direct liquid-liq uid contact between the different phases whereas in the second one sem i-permeable membranes were introduced at the interfaces. The transfer rates measured for Trp and pIPhe at different AOT concentrations show very different behaviors, which are only moderately altered by the pre sence of the semi-permeable membranes. Single uptake and release exper iments, which were independently undertaken show that the rate-determi ning step is the release of the amino acids. A transport mechanism ass uming a competitive release by two processes (droplet opening at the i nterface and ion pair association/dissociation) is proposed. The best separation between the two amino acids is obtained at very low AOT con centrations.