Separation of isomers by ultrafiltration using modified cyclodextrins

In order to improve selective inclusion of cyclodextrin (CD) and permeate f lux, separation of structural isomers (o-, m- and p-nitrophenols) and optic al isomers (D- and L-phenylalanines) were conducted using some modified or and beta-CDs, glucosyl (G1)-, maltosyl (G2)-, hydroxy-propyl (HP)-, alpha- and beta-CDs, according to the previously proposed separation method. Gener ally, rejections of the modified CD are more enhanced than parent alpha-CD and beta-CD by YM1 (molecular weight cut-off (MWCO) of 1000 Da), PLBC (MWCO of 3000 Da) and YM5 (MWCO of 5000 Da) membranes. The G2-beta-CD and HP-bet a-CD are rejected perfectly by YM1 membrane. Rejections of the modified CDs by PLBC and YM5 membranes decrease by more than 20% of those of the YM1 me mbrane. The selectivities of p-nitrophenol to o- or m-nitrophenol are enhan ced with more modified alpha-CDs by YM1 membrane than those of parent alpha -CD. The selectivities decrease the PLBC and YM-5 membranes sharply. Howeve r, no enhancement occurs in the selectivities with modified beta-CDs. L-phe nylalanine is included, which is stronger than D-phenylalanine with all mod ified beta-CDs. Their selectivities are higher than that of the parent beta -CD. We proposed a new recycle system of isomers separation based on these data to apply the method for practical use. (C) 2000 Elsevier Science B.V. All rights reserved.