title: Analysis of flavonoids by non-aqueous capillary electrophoresis with 1-ethyl-3-methylimidazolium ionic-liquids as background electrolytes.
abstract: The separation of three flavonoids, kaempferol, quercetin and luteolin, by capillary zone electrophoresis with three 1-ethyl-3-methylimidazolium ionic liquids (ILs), namely chloride, hydrogen sulfate and tetrafluoroborate salts, under non-aqueous conditions using acetonitrile as solvent was investigated. Depending on the IL, the three flavonoids can be separated under positive voltage with a low IL concentration and negative voltage with a high IL concentration. The separations are based on heteroconjungation between the IL anions and the analytes. The heteroconjungation between the anions of the ILs and the analytes is proton sensitive and only a very small amount of protic solvents, such as methanol, added into the electrolyte solution can harm the separation, but higher IL concentrations can overcome this higher amount of protic solvents. Using a high concentration of IL in the sample was used to enhance the flavonoid solubility by as much as 10, overcoming the problem of the low solubility during NACE analysis with ACN as the solvent. Finally, kaempferol, quercetin and luteolin in Semen Plantaginis were analysed by nonaqueous capillary electrophoresis with low concentration of the hydrogen sulfate ionic liquid with excellent results.
authors.affiliation: Analysis and Testing Centre, Dezhou University, University West Road 566, Dezhou 253023, PR China; Australian Centre for Research on Separation Science, School of Chemistry, University of Tasmania, Hobart, Tasmania 7001, Australia; Institute of Materia Medica, Shandong Academy of Medical Sciences, Jinan 250062, PR China; Key Laboratory of Coordination Chemistry and Functional Materials in Universities of Shandong, Dezhou University, University West Road 566, Dezhou 253023, PR China.
authors.forename: Yuanqi
authors.initials: Y
authors.lastname: Lu
authors.forename: Chunxiao
authors.initials: C
authors.lastname: Jia
authors.forename: Qingqiang
authors.initials: Q
authors.lastname: Yao
authors.forename: Hao
authors.initials: H
authors.lastname: Zhong
authors.forename: Michael C
authors.initials: MC
authors.lastname: Breadmore
mesh_terms: D019075:Electrophoresis, Capillary / Q000379:methods*; D005419:Flavonoids / Q000032:analysis*; D007093:Imidazoles / Q000737:chemistry*; D052578:Ionic Liquids; D012995:Solubility; D012997:Solvents / Q000737:chemistry
chemical_list: D005419:Flavonoids; D007093:Imidazoles; D052578:Ionic Liquids; D012997:Solvents; C518739:1-ethyl-3-methylimidazolium
keywords: Capillary zone electrophoresis; Flavonoids; Ionic liquids; Non-aqueous capillary electrophoresis