Zwitterionic hydrophilic interaction chromatography (ZIC-HILIC) was used to study the retention of selected flavonols. In gel ZIC columns the active layer grafted on polymeric support contains both strongly acidic sulfonic acid groups and strongly basic quaternary ammonium groups in the molar ratio of 1:1, separated by a short alkyl spacer. Retention behavior of the compounds was investigated by varying the separation conditions, e.g. the kind of organic solvent in the mobile phase (acetonitrile or methanol), its ratio to water and pH value. Polar (hydrogen-bonding and dipole-dipole) interactions in the stationary phase are of primary importance, even though weak electrostatic interactions affect the separation of analytes carrying either positive or negative charges.
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