Extremely uniform packing of colloidal silica in capillaries is shown. Reversed-phase electrochromatograms of DiI-C12 exhibit plate heights as low as 0.13 µm and a reduced plate height as low as 0.4, using 75 µm i.d. capillaries packed with 330 nm silica particles. The contribution from the A term is 0±20 nm in electrochromatography. The particles are shown to form colloidal crystals inside the capillaries. Optical images show Bragg diffraction, indicative of crystallinity; SEM images show face-centered cubic crystallinity; and the porosity is 0.25±0.01, which is in agreement with that for face-centered cubic crystals. The capillaries are fritless, and 100 µm i.d. capillaries packed with silica colloidal crystals withstand pressures of at least 12,400 psi.
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