title: Effect of a low-conductivity zone on field-amplified sample stacking in microchip micellar electrokinetic chromatography.
abstract: The effects of a low-conductivity (low-C) zone of an on-line sample preconcentration based on field-amplified sample stacking (FASS) under an acidic condition was investigated in microchip micellar electrokinetic chromatography (MCMEKC).  By employing originally fabricated microchips with T- and cross-channel injectors on a single device, partial injection of the low-C zone and large-volume injection of a sample solution were demonstrated.  As a typical result, the observed peak intensities of the fluorescent dyes were 1.5 - 2.0-fold enhanced by partial injection of the low-conductivity zone, as compared to those in FASS-MCMEKC without injecting the low-C zone; also, 30 - 40-fold enhancements of the detectability were achieved as compared to the conventional MCMEKC analyses.  The resolutions of the hydrophobic analytes were also improved by introducing the low-C zone.  The difference in the retention factors of model analytes in the high-C background and low-C zones was also estimated in order to clarify the effect of the low-C zone on the resolution and detectability in FASS-MCMEKC.
authors.affiliation: Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo, Kyoto, Japan. sueyoshi@anchem.mc.kyoto-u.ac.jp
authors.forename: Kenji
authors.initials: K
authors.lastname: Sueyoshi
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Kitagawa
authors.forename: Koji
authors.initials: K
authors.lastname: Otsuka