Comparison of highly sulfated alpha-, beta-, and gamma-cyclodextrins and 18-crown-6-tetracarboxylic acid for the enantiomeric separation of some amino acids and derivatives by capillary electrophoresis.

18-Crown-6-tetracarboxylic acid (18C6H4) and highly sulfated cyclodextrins (HS-alpha-, beta-, gamma-CDs) are highly selective chiral selectors for the enantioseparation of solutes bearing the primary amino function. Excellent resolutions were obtained for all solutes on HS-gamma-CD and on 18C6H4. The former, however, is by far the best chiral selector for the solutes studied in this work because the highest resolution is obtained with the shortest migration times. The reversal of the D- and L-migration order on HS-CDs compared to 18C6H4 is an interesting feature for the determination of enantiomeric excess.