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High-speed counter-current chromatography (HSCCC) combined with macroporous resin (MR) column was successfully applied to the isolation and purification of four flavonoid glycosides from the medicinal herb Lotus plumule (LP). A polar two-phase solvent system composed of ethyl acetate-n-butanol-water (1:2:3, v/v/v) was selected by high-performance liquid chromatography (HPLC) and run on a preparative scale where the lower aqueous phase was used as the mobile phase with a head-to-tail elution mode. Quercetin-3-O-β-D-glucopyranoside (15 mg), isorhamnetin-3-O-β-D-glucopyranoside (13 mg), apigenin 6-C-β-D-glucopyranosyl-8-C-α-L-arabinopyranoside (18 mg) and apigenin 6,8-di-C-β-D-glucopyranoside (48 mg) were obtained in a one-step HSCCC separation from 240 mg of the sample. The purity of each compound was over 95% as determined by HPLC. Chemical structures of the isolated compounds were identified by electrospray ionization mass spectrometry (ESI-MS-MS) and nuclear magnetic resonance (NMR) methods. Moreover, the four compounds were isolated from LP for the first time., (© The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The liquid chromatographic retention behavior of nineteen monoaromatic chlorophenols on a beta-cyclodextrin bonded-phase column is investigated with respect to mobile phase composition, pH, temperature, and ionic strength. The mechanistic aspects of retention of these compounds on the beta-cyclodextrin column are studied and compared to other reversed-phase columns. Most of the evidence suggests that the unique selectivity of this column is due to inclusion complex formation, which provides the physical basis for the resolution of positional isomers. Under certain chromatographic conditions, however, the more highly chlorinated congeners appear to be excluded from the cyclodextrin cavity; in such cases a normal-phase chromatographic mechanism is postulated, based on the interaction of the substrates with the secondary hydroxyls on the periphery of the cyclodextrin moieties.

The liquid chromatographic separation of 19 monoaromatic chlorophenols on a beta-cyclodextrin bonded-phase column is investigated in both an isocratic and a gradient elution mode. Even though the isocratic mode can be employed for the separation of the member components of each category of chlorophenols (e.g., mono-, di-, etc.), significant overlaps between the retention times of the various categories prevent the separation of all chlorophenols on a single chromatogram. Gradient elution can be used, however, for the separation of 15 of the 19 chlorophenol isomers. The unique features of gradient elution as applied to beta-cyclodextrin bonded-phase columns are discussed. The detection of chlorophenols with UV and electrochemical methods is also discussed and the two are compared.