The bridged β-cyclodextrin has been widely used as artificial enzymes due to its synergistic inclusion effect and unique multi-recognition function. In this paper, we employed bridged β-cyclodextrin as ligand in order to explore its chiral separation function. A novel N,N'-ethylenediamino bridged bis(β-cyclodextrin)-bonded SBA-15 chiral stationary phase (BCDSP) for HPLC was first developed by solid successive reaction method. In the first step, a 6-O-toluene-sulfonyl-β- cyclodextrin was bonded to ordered mesoporous SBA-15 by using 3-isocyanatopropyltriethoxysilane as coupling reagent. Then the bonded SBA-15 silica continued to react with mono-(6-ethylenediamino-6-deoxy)-β-cyclodextrin and obtained the BCDSP with bridged double β-cyclodextrin ligand. Its chemical structure was characterized by mass spectrometry, infrared spectroscopy, elemental analysis, thermogravimetric analysis and transmission electron microscopy. The basic chromatographic property of new stationary phase was evaluated in polar organic mode and used for the separations of β-blockers enantiomers. Some effect factors such as the concentrations of organic solvent, triethylamine (TEA) and glacial acetic acid (HOAc) in mobile phase, column temperature on the resolution were investigated. The 14 kinds of β-blockers enantiomers on BCDSP column were successfully separated under the optimized chromatographic conditions, in which the resolutions of propranolol enantiomers and carvedilol enantiomers were 2.18 and 2.01 within 10～20 min, respectively. By comparative study, the bis(β-cyclodextrin)-bonded phase could separate all 14 kinds of β-blockers enantiomers, while native β-cyclodextrin-bonded phase (CDSP) with single ring ligand could partially resolve about 4 kinds of them under optimized condition. Moreover, the resolutions of drugs on BCDSP were more than those on native β-cyclodextrin column. The chromatographic data analysis showed that BCDSP with double β-cyclodextrin ligand exhibited a stronger enantioseparation ability and wider analytes as comparison with the native β-cyclodextrin stationary phase. The excellent property of BCDSP should be due to the double β-cyclodextrin ligand expands the chiral recognization for enantiomers of drugs. Meanwhile, the inclusion interaction from double cavities and the hydrogen bonding interaction from the bridged ethylenediamino group with the tested enantiomers improved the chiral selectivities of β-blockers. The ordered pore of SBA-15 could also reduce the mass transfer resistance and enhance the chiral chromatographic property of BCDSP. According to chromatographic data, the similarities and differences of separation mechanism of double β-cyclodextrin and single β-cyclodextrin stationary phases were discussed. On the one hand, the inclusion complexing and hydrogen bonding interactions of BCDSP played important roles in chiral separations, which was similar to the common single-β-cyclodextrin stationary phase. On the other hand, the synergistic interaction of double β-cyclodextrin cavities could expand spatial recognition domain, making BCDSP with better chiral chromatographic performance, wider analytes, higher resolution and shorter analysis time. This new stationary phase has clear and stable structure of ligand, convenient preparation method, lower cost, especially, its excellent enantioseparation ability. The exploration of this double β-cyclodextrin-bonded phase could provide a kind of new type separation material for wide chiral drugs. It has a research significance and bright prospect in quality-controlling of chiral drugs.

Key words: high performance liquid chromatography, ethylenediamino bridged bis(β-cyclodextrin)-bonded SBA-15 chiral stationary phase, synergistic separation mechanism, β-blockers, chiral drugs