title: Separation and on-line preconcentration by stacking and sweeping of charged analytes in the plant by microemulsion electrokinetic chromatography with nonionic surfactants.
abstract: A novel on-line technique for stacking and sweeping of long sample plugs with simultaneous determination of charged analytes in the plant (protocatechuic aldehyde, rosmarinic acid, danshensu, salvianolic acid B, and protocatechuic acid) by the nonionic microemulsion electrokinetic chromatography (MEEKC) is presented. The preconcentration efficiency provided about 9-28-fold for stacking and 7-14-fold for sweeping in the enhancements of LOD. The effects of oil phase, Brij-35 and buffer concentrations on stacking and sweeping efficiency were examined in order to optimize the two methods. In nonionic MEEKC, the effect of the type of oil and buffer contents on preconcentration mechanism is often sophisticated. This study had demonstrated that the oil type and buffer content in nonionic microemulsion indeed markedly altered the affinity of microemulsion with analytes. Finally, in comparison to the stacking method, the most apparent disadvantages of the sweeping method were the relatively high limits of detection and poor peak shapes.
authors.affiliation: Key Laboratory of Modern Chinese Medicines, China Pharmaceutical University, Nanjing 210009, People's Republic of China. caojun91@163.com
authors.forename: Jun
authors.initials: J
authors.lastname: Cao
authors.forename: Lian-Wen
authors.initials: LW
authors.lastname: Qi
authors.forename: E-Hu
authors.initials: EH
authors.lastname: Liu
authors.forename: Wei-Dong
authors.initials: WD
authors.lastname: Zhang
authors.forename: Ping
authors.initials: P
authors.lastname: Li
mesh_terms: D002021:Buffers; D002845:Chromatography / Q000379:methods; D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods*; D004655:Emulsions; D005240:Feasibility Studies; D006863:Hydrogen-Ion Concentration; D062385:Hydroxybenzoates / Q000032:analysis*; D009821:Oils / Q000737:chemistry; D009862:Online Systems; D018517:Plant Roots / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D012015:Reference Standards; D027544:Salvia / Q000033:anatomy & histology / Q000737:chemistry*; D012680:Sensitivity and Specificity; D012996:Solutions / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D002021:Buffers; D004655:Emulsions; D062385:Hydroxybenzoates; D009821:Oils; D012996:Solutions; D013501:Surface-Active Agents; D011092:Polyethylene Glycols; C017616:phenolic acid; C515901:Brij 35