Preparation of a stilbene diamido-bridged bis(β-cyclodextrin)-bonded chiral stationary phase for enantioseparations of drugs and pesticides by high performance liquid chromatography

A stilbene diamido-bridged bis(β-cyclodextrin) was synthesized via the reaction between 4,4′-stilbene dicarboxylic acid and 6-deoxy-6-amino-β-cyclodextrin. Then it was bonded onto the surface of an ordered mesoporous SBA-15 to obtain a novel bridged bis(β-cyclodextrin)-bonded chiral stationary phase (SBCDP). The structures of the bridged bis(β-cyclodextrin) and SBCDP were characterized by the mass spectrometry, nuclear magnetic resonance, infrared spectroscopy, elemental analysis and thermogravimetric analysis. The chromatographic performance of SBCDP was systematically evaluated by separating 23 racemic drugs and pesticides, including trimeprazine, praziquantel, flavanones, β-blockers and triazole pesticides in the reversed-phase chromatography or the polar organic mode. The chromatographic conditions that affect the enantioselectivity or diasterioselectivity of SBCDP were investigated in detail, including the mobile phase composition, pH value and column temperature. As a result, all tested analytes were resolved on SBCDP with high resolutions (1.51∼5.15) within about 25 min, and the enantioseparation resolutions of flavanone and imazalil were up to 5.15 and 4.38, respectively. Compared with the native β-cyclodextrin stationary phase (CDCSP), the SBCDP had a better chromatographic performance in enantioselectivity and diasterioselectivity. For example, enantiomers of trimeprazine, praziquantel, flavanone and imazalil those could not be separated by CDCSP, were separated by SBCDP with high resolutions. Unlike the small cavity (0.65 nm) of native CD, the bridging linker of the bridged bis(β-CD) supplied a well-organized “pseudo-cavity”, and combined two native CDs as an organic whole, which could synergistically encapsulate and complex some bulky analytes, making the chiral discrimination of SBCDP more precise. Moreover, we also found that SBCDP possessed high enantioselectivity and diastereoselectivity over a wide range of temperature (30∼60°C), which made the fast analysis possible. As a new chiral separation material, SBCDP may have wider applications in analysis of chiral compounds.