Sol-gel technique for the preparation of β-cyclodextrin derivative stationary phase in open-tubular capillary electrochromatography

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Abstract
A novel open‐tubular capillary electrochromatography (OT‐CEC) column coated with 2,6‐dibutyl‐β‐cyclodextrin (DB‐β‐CD) was prepared using sol‐gel technique. In the sol‐gel approach, owing to the three‐dimensional network of sol‐gel and the strong chemical bond between the stationary phase and the surface of capillary columns, good chromatographic characteristics and unique selectivity in separating isomers were shown. We achieved high efficiencies of 5–14×104 plates/m for the isomeric nitrophenols using the sol‐gel‐derived DB‐β‐CD columns. The migration time reproducibility of the separation of the isomeric nitrophenols was better than 2.2% over five runs and 4.5% from column to column. These sol‐gel‐coated DB‐β‐CD columns have shown improved separations of isomeric aminophenols, isomeric dihydroxybenzenes and isomeric nitrophenols, in comparison with the sol‐gel matrix capillary column. The influences of buffer pH and methanol solvent on separation were investigated. The chiral resolution of enantiomers such as ibuprofen and binaphthol was explored primarily.