Capillary Electrophoretic Resolution of Enantiomers of Aromatic Amino-Acids with Highly Sulfated α-, β- and γ-Cyclodextrins

Abstract

Using cyclodextrin capillary electrokinetic chromatography (CD-EKC), baseline separation of aromatic amino acids was achieved. The variations in amino acids side chain, in the nature of the aromatic moiety and its substitution, and their derivatives at the amino or carboxylic terminal provide an ideal model for the systematic study of the structural interactions with the chiral selectors:anionic cyclodextrins (highly sulfated-CD or highly S-CD). The use of negatively charged cyclodextrins provides a driving force in the opposite direction of the positively charged or neutral molecules in the running buffer and enantiomeric resolution by inclusion of compounds in the CD cavity. The complete resolution was obtained using 25 mM phosphate buffer at pH 2.5 containing 3 (w/v) of highly S-CD at 25 °C with a applied field of 0.30 kV cm−1 with capillaries dynamically coated with polyethylene oxide (PEO). A comparison was possible to investigate the structural arrangement responsible for regiospecific interactions with the enantiomers of the different amino acids.