title: Application of 1-alkyl-3-methylimidazolium-based ionic liquids as background electrolyte in capillary zone electrophoresis for the simultaneous determination of five anthraquinones in Rhubarb.
abstract: A capillary zone electrophoresis method using only 1-alkyl-3-methylimidazolium-based ionic liquids as background electrolyte for the simultaneous determination of five anthraquinone derivatives including aloe-emodin, emodin, chrysophanol, physcion and rhein in Rhubarb species was described. Ion association constants, K(ass), between anthraquinone anions and imidazolium cations were determined by analyzing the electrophoretic mobility change of anthraquinone anions using a non-linear least-squares method and factors contributing to ion associability were systematically clarified. For method optimization, several parameters such as ionic liquids concentration, background electrolyte pH and applied voltage, on the separation were evaluated and the optimum conditions were obtained as follows: 90mM 1-butyl-3-methylimidazolium tetrafluoroborate (pH 11.0) with an applied voltage of 20kV. Under these conditions, the method has been successfully applied to the determination of anthraquinones in extracts of two kinds of Rhubarb plants (R. palmatum and R. hotaoense) within 12min. The method proposed herein was shown to be much simpler than the previously reported methods.
authors.affiliation: Department of Chemistry, Lanzhou University, Lanzhou, China; State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, China.
authors.forename: Kan
authors.initials: K
authors.lastname: Tian
authors.forename: Yushang
authors.initials: Y
authors.lastname: Wang
authors.forename: Yonglei
authors.initials: Y
authors.lastname: Chen
authors.forename: Xingguo
authors.initials: X
authors.lastname: Chen
authors.forename: Zhide
authors.initials: Z
authors.lastname: Hu