Electrodialysis system for large-scale enantiomer separation

In contrast to analytical methods, the range of technologies currently appl ied for large-scale enantiomer separations is not very extensive. Therefore , a new system has been developed for large-scale enantiomer separations th at can be regarded as the scale-up of a capillary electrophoresis system. I n this stacked membrane system, chiral selectors that are retained by size- selective membranes are used. Upon application of an electrical potential, selective transport of the free enantiomer will occur, thus providing separ ation. In principle, this system can handle the same extensive range of ena ntiomers that can be separated in capillary electrophoresis systems on an a nalytical scale. In a system containing four separation compartments, alpha -cyclodextrin has been used as a chiral selector to separate D,L-Trp. Base d on a transport model, a factorial design is used to investigate the effec ts of various process parameters. The results show that the addition of met hanol is of minor influence, whereas the pH has a major effect, both on the operational selectivity and on the transport number. Experiments with AgNO 3 as the background electrolyte showed that the operational selectivity has a plateau value of 1.08 at a pH ranging from 3 to 6. Because of the ease o f scale-up of electrodialysis processes, this operational selectivity will allow for the separation of enantiomers on a large scale.