title: Comparison of two sample preconcentration strategies for the sensitivity enhancement of flavonoids found in Chinese herbal medicine in micellar electrokinetic chromatography with UV detection.
abstract: Two on-column preconcentration techniques named stacking with reverse migrating micelles (SRMM) and anion selective electrokinetic injection and a water plug-sweeping with reverse migrating micelles (ASIW-sweep-RMM) were used and compared for concentration and separation of flavonoids in Chinese herbs using reverse migration micellar electrokinetic chromatography (RM-MEKC). The optimal background electrolyte (BGE) used for separation and preconcentration was a solution composed of 20mM phosphoric acid (H(3)PO(4))-100mM sodium dodecyl sulfate (SDS)-20% (v/v) acetonitrile (ACN) buffer (pH 2.0), the applied voltage was -15kV. To achieve reasonable results of the two techniques, the conditions which affected preconcentration were examined. A comparison of used techniques with normal hydrodynamic injection (5s), concerning enhancement factors and limits of detection (LODs) was presented. Under the optimum stacking conditions, about 27-37- and 45-194-fold improvement in the detection sensitivity was obtained for SRMM and ASIW-sweep-RMM, respectively, compared to usual hydrodynamic sample injection (5s). The LODs (S/N=3) for SRMM and ASIW-sweep-RMM in terms of peak height, can reach down to 1.15 x 10(-2) microg/ml for hesperetin and 2.4 x 10(-3) microg/ml for nobiletin, respectively. Finally, the amounts of the six flavonoids in extract of Fructus aurantii Immaturus were successfully determined using ASIW-sweep-RMM. The six analytes were baseline separated with sample matrix under the optimum ASIW-sweep-RMM conditions and the experimental results showed that preconcentration was well achieved after the dilution of sample solutions.
authors.affiliation: State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, China.
authors.forename: Jinhua
authors.initials: J
authors.lastname: Zhu
authors.forename: Kai
authors.initials: K
authors.lastname: Yu
authors.forename: Xingguo
authors.initials: X
authors.lastname: Chen
authors.forename: Zhide
authors.initials: Z
authors.lastname: Hu
mesh_terms: D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods*; D002957:Citrus / Q000737:chemistry; D004365:Drugs, Chinese Herbal / Q000032:analysis*; D005419:Flavonoids / Q000032:analysis* / Q000302:isolation & purification; D015203:Reproducibility of Results; D013056:Spectrophotometry, Ultraviolet; D035501:Uncertainty
chemical_list: D004365:Drugs, Chinese Herbal; D005419:Flavonoids