Submicrometer plate heights for capillaries packed with silica colloidal crystals.

Extremely uniform packing of colloidal silica in capillaries is shown. Reversed-phase electrochromatograms of DiI-C(12) exhibit plate heights as low as 0.23 microm and a reduced plate height as low as 0.7, using 75 microm 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. Scanning electron microscopy (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 microm i.d. capillaries packed with silica colloidal crystals withstand pressures of at least 12,400 psi.