Capillary electrophoretic separation of binaphthyl enantiomers with two polymeric chiral surfactants: H-1-nuclear magnetic resonance and fluorescencespectroscopy study

The use of the water-soluble polymeric chiral surfactants (PCS), sodium N-u ndecanoyl-L-valinate (poly-L-SUV) and sodium undecanoyl-L-isoleucinate (pol y-L-SUI) as buffer additives in electrokinetic chromatography (EKC) afforde d the separation of racemic mixtures of 2,2'-dihydroxy-1,1'-binaphthyl (BOH ) and 1,1'-binaphthyl-2,2'-diyl hydrogen phosphate (BNP). The apparent bind ing constants of the PCS to the enantiomers of BNP and BOH were obtained th rough H-1-nuclear magnetic resonance (H-1-NMR) titrations and fluorescence spectroscopy, respectively. The H-1-NMR titration studies show that the BNP enantiomers are localized in the hydrophobic micellar pockets of PCS and f orm complexes of a 1:1 stoichiometry. The binding constants of PCS of BOH w ere determined from a Benesi-Hildebrand treatment of the fluorescence data. The EKC data corroborate those of the binding constants, supporting the fo rmation of inclusion complexes. A model rationalizing the chiral discrimina tion of the enantiomers of BNP is proposed based on the intermolecular inte ractions observed in H-1-NMR data.