Performance of laterally elongated pillar array columns in capillary electrochromatography mode

Area of Science:

• Analytical Chemistry
• Separation Science
• Microfluidics

Background:

• Capillary electrochromatography (CEC) is a powerful separation technique combining principles of capillary electrophoresis and liquid chromatography.
• Microfabricated column structures are crucial for enhancing CEC performance, particularly in microchip devices.
• Understanding dispersion effects, such as sidewall contributions, is key to optimizing separation efficiency.

Purpose of the Study:

• To investigate the performance of cylindrical and laterally elongated pillar array columns for CEC.
• To quantify the impact of sidewall effects on dispersion and plate height.
• To evaluate the potential of different pillar geometries for microchip CEC.

Main Methods:

• Fabrication and testing of cylindrical and rectangular (laterally elongated, aspect ratio 4) pillar array columns.
• Determination of minimal theoretical plate heights using coumarin C440 under unretained conditions.
• Analysis of dispersion across the entire channel width versus the central zone.
• Kinetic plot analysis considering a maximum operating voltage of 20 kV.

Main Results:

• Minimal theoretical plate heights of 1.90 μm (cylindrical) and 1.46 μm (rectangular) were achieved without sidewall effects.
• Sidewall-related dispersion was found to significantly contribute to overall dispersion.
• A 40% reduction in plate height was observed when considering only the central channel zone.
• Rectangular pillars demonstrated higher efficiency compared to cylindrical pillars.

Conclusions:

• Laterally elongated rectangular pillar array columns provide superior efficiency in CEC compared to cylindrical designs.
• Minimizing sidewall effects is critical for achieving high-efficiency separations in microchip CEC.
• The studied rectangular pillar geometry represents a promising advancement for microchip capillary electrochromatography.