Cyclodextrin-functionalized silica nanoparticles with dendrimer-like spacers for enantioselective capillary electrochromatography

In this report, beta-cyclodextrin (beta-CD)-functionalized silica nanoparticles (SNPs) with dendrimer-like spacers were synthesized by first grafting the SNPs with different generations of polyamidoamines (PAMAMs), followed by modifying the grafted SNPs with mono-6-deoxy-(p-tolylsulfonyl)-beta-CD. The beta-cyclodextrin-modified silica nanoparticle-cored PAMAMs (SNP-PAMAM-beta-CDs) were studied as chiral pseudostationary phases for separating three racemic drugs, namely, chlorpheniramine, nefopam, and verapamil. The beta-CD-functionalized SNPs with dendrimer-like spacers were more enantioselective than native beta-CD, and the structures of the dendritic spacers were highly influential on the separation. In 20 mM NaH2PO4, addition of 4.00 mg/mL SNP-G1.0-beta-CD (corresponding to 1.12 mM beta-CD) could baseline separate the enantiomers of chlorpheniramine and nefopam, and introduction of 7.00 mg/mL SNP-G0-beta-CD (corresponding to 1.68 mM beta-CD) resulted in enantioseparation of the verapamil racemates. On the contrary, the enantiomers of nefopam and verapamil could not be resolved in the presence of 15 mM native beta-CD. Our results suggest that SNP-PAMAM-beta-CDs hold great promise for enantioselective separations.