Physically adsorbed chiral stationary phase of avidin on monolithic silica column for capillary electrochromatography and capillary liquid chromatography

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Abstract
The physical adsorption method proposed previously has been successfully applied to a monolithic silica column. By virtue of the physical adsorption, a chiral stationary phase of avidin was prepared onto the silica monolith. The phase ratio of resulting stationary phase was evaluated with frontal analysis. The method proved to be comparable in phase ratio to the chemical bonding methods used in high‐performance liquid chromatography (HPLC). Enantiomer separations were carried out in capillary electrochromatography (CEC) and capillary liquid chromatography (CLC) modes. Due to its larger phase ratio, the resulting column showed more powerful separation capability as compared to open‐tubular CEC (OTCEC). Twelve chiral compounds were baseline‐resolved. The resulting column showed high separation efficiency, with average theoretical plate numbers of 66 000/m for CLC and 122 000/m for CEC. Good reproducibility was observed, with RSD value less than 1.3% for retention time, retention factor and separation factor, and less than 6.6% for plate counts and resolution (n = 40). Fast separations were achieved with a short column. The test enantiomers were baseline‐resolved within 4 min under CLC and CEC modes. In addition, field‐enhanced sample injection (FESI) was coupled to CLC as well as CEC to improve the detection sensitivity.