title: Polarity, selectivity and performance of hydrophilic organic/salt-containing aqueous two-phase system on counter-current chromatography for polar compounds.
abstract: The essential attributes of a solvent system for separation polar compounds on CCC are polarity, selectively and performance. Here, hydrophilic organic/salt-containing aqueous two-phase system (HO/S TPS) was evaluated as an alternative solvent system for CCC separation of polar compounds. Polarity measurements based on Rohrschneider-Snyder parameter was developed as quantitative assessing the polarity of HO/S TPS and comparing with an organic/aqueous system. All investigated 1-butanol/ethanol/saturated ammonium sulfate solution/water (BEAsWat) and 1-butanol/ethanol/saturated dipotassium hydrogen phosphate solution/water (BEDhpWat) systems with polarity values of organic phase from 4.5 to 6.8, were more polar than chloroform/methanol/water (1/1/1). The considerable water content of BEAsWat and BEDhpWat (0/1/1/1/) was 45.4 and 42.6% (w%) of hydrophilic organic phase, and 66.4 and 51.2% (w%) of salt-containing aqueous phase, respectively, closed to conventional aqueous two-phase system. Therefore, the polarity of HO/S TPS is in the middle of organic/aqueous and aqueous two-phase system. The LogKC values of twenty four polar compounds as model mixture confirmed that the polarities of HO/S TPSs were matched to that of the polar compounds and shown to be a very selective technique capable of separating positional isomers. Moreover, BEAsWat and BEDhpWat systems can be easily retained in CCC column with suitable elution mode. The hydrodynamic behavior reversion of HO/S TPS on hydrodynamic CCC was observed and was tentatively explained based on the density difference. Finally, caffeoylquinic acid isomers and dihydroxybenzoic acid isomers were successfully separated with HO/S TPS on CCC, respectively. Those results demonstrate that HO/S TPS on CCC is a performant and stable way to separate polar compounds from natural products.
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Liu
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China.
authors.forename: Zhilai
authors.initials: Z
authors.lastname: Hong
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China.
authors.forename: Mingzhe
authors.initials: M
authors.lastname: Gao
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China.
authors.forename: Zhixin
authors.initials: Z
authors.lastname: Wang
authors.affiliation: National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Gu
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China.
authors.forename: Xiaozhe
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China; Beijing University of Chinese Medicine, Beijing, China. Electronic address: hbxiao69@163.com.
authors.forename: Hongbin
authors.initials: H
authors.lastname: Xiao
mesh_terms: D020001:1-Butanol / Q000737:chemistry*; D000645:Ammonium Sulfate / Q000737:chemistry*; D002725:Chloroform / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003377:Countercurrent Distribution / Q000379:methods*; D000431:Ethanol / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D000432:Methanol / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry*; D012997:Solvents; D014867:Water / Q000737:chemistry
chemical_list: D010710:Phosphates; D010936:Plant Extracts; D017680:Potassium Compounds; D012997:Solvents; D014867:Water; D000431:Ethanol; D002725:Chloroform; D020001:1-Butanol; C013216:potassium phosphate; D000645:Ammonium Sulfate; D000432:Methanol
keywords: Counter-current chromatography; Hydrophilic compounds; Hydrophilic organic/salt-containing aqueous two-phase system; Polarity; Selectivity