Enantioselective open-tubular capillary electrochromatography using a β-cyclodextrin–gold nanoparticles–polydopamine coating as a stationary phase

A novel enantioselective open-tubular capillary electrochromatography (OT-CEC) technique was developed employing thiol β-cyclodextrin (SH-β-CD) conjugated polydopamine–gold nanoparticles (PDA–AuNPs) as a stationary phase. The capillary inner surface was functionalized with dopamine by self-polymerization under alkaline conditions and the subsequent introduction of gold nanoparticles based on the electrostatic interaction and affinity between gold nanoparticles and amine groups on polydopamine. Then, thiol β-cyclodextrin was introduced on the gold nanoparticle layer through S–Au covalent bonding. The preparation conditions including dopamine concentration, the number of coating layers of gold nanoparticles and thiol β-cyclodextrin concentration were optimized to obtain satisfactory enantioselectivity. Scanning electron microscopy (SEM), energy dispersive X-ray analysis spectroscopy (EDS) and EOF experiments were carried out to characterize the prepared open tubular (OT) column. Then, the separation effectiveness of the open tubular column was verified by the separation of seven chiral drugs including tryptophan, phenylalanine, histidine, fexofenadine, promethazine, tropicamide and terbutaline, and satisfactory separation results were obtained for the analytes studied. Moreover, the stability and repeatability of the column were studied through intra-day, inter-day and column-to-column investigations.