Performance Evaluation of Different Design Alternatives for Microfabricated Nonporous Fused Silica Pillar Columns for Capillary Electrochromatography

An experimental study comparing the performance of different designs for microfabricated column structures for microchip capillary electrochromatography is presented. The work is a follow-up to our previously published modeling and simulation study on the same topic. Experiments were performed using fused silica microchips with and without octadecyltrimethoxysilane coating for nonretained and retained modes of operation, respectively. Showing the same trends as the modeling results, the foil shape produces a significant decrease in plate height with an increase of around 15% in mobile phase velocity in nonretained measurements of Coumarin 480 (C480). Measured plate heights at 1 kV/cm applied electric field were 0.77, 1.33, and 1.42 μm for foil, diamond, and hexagon, respectively. Chromatographic runs of C480 yielded minimal plate height values of 1.85 and 3.28 μm for foil and diamond, respectively. The optimization of the shape and placement of the structures appeared to have a considerable impact on the achievable performance.