C-Term Reduction in 3 μm Open-Tubular High-Aspect-Ratio Channels in AC-EOF Vortex Chromatography Operation

Abstract

The performance of liquid chromatography operation in open-tubular channels, the ideal chromatographic column format, is limited by slow mass transport between the mobile and stationary phase. We recently introduced a lateral mixing methodology (“vortex chromatography”) to reduce Taylor–Aris dispersion by employing (small) AC-EOF (alternating current electroosmotic flow) fields oriented perpendicular to the conventionally applied, axially oriented pressure gradient, resulting in the reduction of the C-term by a factor of 3, studied in 40 × 20 μm2 (aspect ratio (AR) = 2) channels under unretained conditions. In the present contribution, a further increased performance gain for channel dimensions relevant for chromatographic applications is demonstrated. The impact of the applied voltage and salt concentration is studied for 3 × 20 and 5 × 20 μm2 channels in ARs of up to 6.7, revealing a C-term reduction potential of a factor of up to 5 for large molecules (dextran) under unretained conditions. The decrease in κaris in a 5 μm channel (reduction of 80%) was larger than the decrease in a 3 μm channel (reduction of 44%).

AC Electrothermal Effect Promotes Enhanced Solute Mixing in a Wavy Microchannel

“…In addition, it has been shown that the three-dimensional (3D) chaotic streamlines produced by the coupling of pressure-driven and electroosmotic flow caused by the patterned electrodes can decrease axial dispersion . According to recent experimental work, the AC electroosmotic flow can minimize Taylor–Aris dispersion even further by generating vortices in open-tubular microfluidic channels while subjected to an axial pressure gradient . In this microfluidic system, the use of DC-electroosmotic vortices increases the strength of axial flow and reduces the separation of two species by a factor of 50 .…”

“…35 According to recent experimental work, the AC electroosmotic flow can minimize Taylor−Aris dispersion even further by generating vortices in open-tubular microfluidic channels while subjected to an axial pressure gradient. 36 In this microfluidic system, the use of DCelectroosmotic vortices increases the strength of axial flow and reduces the separation of two species by a factor of 50. 37 Furthermore, many biological liquids exhibit viscoelastic behavior.…”