Comparison of alkylglycoside surfactants in enantioseparation by capillary electrophoresis

Three alkylglycoside surfactants, namely n-octyl-beta-D-glucopyranoside (OG), n-nonyl-beta-D-glucopyranoside (NG), and n-octyl-beta-D-maltopyranoside (OM), were compared in the enantiomeric separation of dansyl amino acids, binaphthyl phosphate, bupivacaine and warfarin. While only OM exhibited an enantioselectivity toward warfarin, bupivacaine, and dansyl tryptophan, all three surfactants were effective in the enantiomeric resolution of napthyl phosphate and other dansyl amino acids. With the exception of naphthyl phosphate, which could be resolved enantiomerically with OM at surfactant concentrations below the CMC, all solutes required surfactant concentrations greater than the CMC value. This was attributed to the strong hydrophobic association of napthyl phosphate with the OM monomers and to the presence of maltoside residue in the OM surfactant. In general, the optimum surfactant concentration needed for maximum enantiomeric resolution was an inverse function of the hydrophobic character of the solute. Under a given set of conditions, the enantiomeric resolution exhibited by the alkylglycoside surfactants was largely influenced by the extent and loci of solute solubilization into the micelle, and by the nature of the chiral sugar head group of the surfactant.