A new on-line concentration method of cationic molecules in capillary electrophoresis by a hyphenated micelle to solvent stacking coupling with large amount sample electrokinetic stacking injection

In this paper, we established a new on-line method using micelle to solvent stacking (MSS) technique combining with large amount sample electrokinetic stacking injection (LASEKSI) for the analysis of cationic molecules. In this MSS–LASEKSI, by modulating the integral EOF across the capillary, a equilibrium state was formed and can be maintained for a long time, leading to the continuous stacking of the analytes on the basis of MSS. Thereby, an extremely large amount sample was permitted to be injected into the capillary and then an improved enrichment fold can be achieved comparing with the each case. The variables affecting the performance of MSS–LASEKSI were investigated and discussed. Under the optimized conditions, 6.3 × 103- and 6.4 × 102-fold enrichment in peak heights upon normal CZE method (injected at 0.5 psi for 3 s) and number of plates of 2.9 × 106 and 6.5 × 105 were attained for berberine and theophylline, respectively. The developed method described here may provide prospects for exploiting a new concentration technique to achieve higher enrichment factor.

► This paper builds a hyphenated MSS enrichment technique coupling with LSAEKSI for CE.
► 6.3 × 103-fold enrichment in peak height was obtained under the optimum conditions.
► This method provides prospects to achieve higher enrichment fold.