Sweeping with Electrokinetic Injection and Analyte Focusing by Micelle Collapse in Two-Dimensional Separation via Integration of Micellar Electrokinetic Chromatography with Capillary Zone Electrophoresis

摘要

ABSTRACT: A novel integrated concentration/separation approach in-nvolving online combination of sweeping with electrokinetic injection andnanalyte focusing by micelle collapse (AFMC) with heart-cutting two-ndimensional (2D) capillary electrophoresis (CE) in a single capillary wasndeveloped for analysis ofHerba Leonuri andmouse blood samples. First, annew sweeping with an electrokinetic injection preconcentration methodnwas developed to inject a large volume sample solution and significantlynenhance detection sensitivity. Then, the preconcentration scheme wasnintegrated to the 2D-CE to provide significant analyte concentration andnextremely high resolving power. The sample was preconcentrated bynsweeping with electrokinetic injection and separated in first dimensionnmicellar electrokinetic chromatography (MEKC). Then, only a desirablenfraction of the first dimension separation was transferred into the second dimension of the capillary by pressure and further analyzednby capillary zone electrophoresis (CZE) acting as the second dimension. As the key to successful integration ofMEKC and CZE, annAFMC step was integrated between the two dimensions to release analytes from the micelle interior to a liquid zone and tonovercome the sample zone diffusion caused by mobilization pressure. The injected sample plug lengths for flavonoids under 15 kVnfor 60 min were experimentally estimated as 546 cm. The dual concentration methods resulted in the increased detection factors ofn6000-fold relative to the traditional pressure injection method. The relative standard deviation (RSD) values of peak height, peaknarea, andmigration time were 2.7-4.5%, 1.9-4.3%, and 4.7-6.8% (n = 10), respectively. The limits of detection (S/N = 3) were innthe range of 7.3-36.4 ng/L, and the theoretical plate numbers (N) were in the range of 1.7-4.3 u0001 104nplates/m. This method hasnbeen successfully applied to determine flavonoids in Herba Leonuri and postdosing mouse blood samples. The pharmacokineticnstudy also demonstrated that the proposed concentration/separation method was convenient and sensitive and would become annattractively alternative method for online sample concentration and separation in complex samples.