Liquid-liquid/solid three-phase high-speed counter-current chromatography based on O-carboxymethyl chitosan-functionalized multi-walled carbon nanotubes as solvent additive

O-Carboxymethyl chitosan-functionalized multi-walled carbon nanotubes (MWCNTs/OMCS) were found to be a novel additive for high-speed counter-current chromatography (HSCCC). It was shown that a kind of liquid-liquid/solid (LLS) three-phase HSCCC system can be established with MWCNTs/OMCS as additive, and in this HSCCC system liquid-liquid partition chromatography and liquid-solid adsorption chromatography were combined. This study revealed that MWCNTs/OMCS can obviously improve peak resolution (R-s). Three flavonol aglycons (quercetin, luteolin and kaempferol) were used as model analytes to study the mechanisms of MWCNTs/OMCS as HSCCC solvent additive to improve Rs. It was indicated that MWCNTs/OMCS improved R-s not by increasing the stationary phase retention but by introducing intermolecular forces: electrostatic interaction, hydrogen bonding interaction and pi-pi conjugation.