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Sample preconcentration by field amplification stacking for microchip‐based capillary electrophoresis
Author(s) -
Lichtenberg Jan,
Verpoorte Elisabeth,
de Rooij Nico F.
Publication year - 2001
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/1522-2683(200101)22:2<258::aid-elps258>3.0.co;2-4
Subject(s) - stacking , capillary electrophoresis , analyte , electrophoresis , fluidics , microfluidics , capillary action , spark plug , analytical chemistry (journal) , signal (programming language) , chemistry , chromatography , materials science , nanotechnology , computer science , organic chemistry , composite material , engineering , programming language , aerospace engineering
A microchip structure for field amplification stacking (FAS) was developed, which allowed the formation of comparatively long, volumetrically defined sample plugs with a minimal electrophoretic bias. Up to 20‐fold signal gains were achieved by injection and separation of 400 μm long plugs in a 7.5 cm long channel. We studied fluidic effects arising when solutions with mismatched ionic strengths are electrokinetically handled on microchips. In particular, the generation of pressure‐driven Poiseuille flow effects in the capillary system due to different electroosmotic flow velocities in adjacent solution zones could clearly be observed by video imaging. The formation of a sample plug, stacking of the analyte and subsequent release into the separation column showed that careful control of electric fields in the side channels of the injection element is essential. To further improve the signal gain, a new chip layout was developed for full‐column stacking with subsequent sample matrix removal by polarity switching. The design features a coupled‐column structure with separate stacking and capillary electrophoresis (CE) channels, showing signal enhancements of up to 65‐fold for a 69 mm long stacking channel.