Electrochromatography in packed tubes using 1.5 to 50 μm silica gels and ODS bonded silica gels

Summary Electrochromatography (that is HPLC where the eluent is driven along the column by electro-osmosis using fields of up to 100 kV m⁻¹) promises plate efficiencies for HPLC which are comparable to those attained in capillary gas chromatography, but this requires that narrow-bore columns can be successfully packed with submicron particles. This paper demonstrates that we have now moved a considerable distance towards this goal. We show (1) that, following theory, there is no evidence of any reduction in electroosmotic velocity in columns packed with particles down to 1.5 μm diameter, (2) that reduced plate heights as low as unity are attainable for unretained solutes using both slurrypacked and drawn-packed columns 30 to 200 μm bore and up to 1 m long when packed with conventional 3 and 5 μm silica gels or with 1.5 μm impermeable silica spheres, (3) that columns driven electrically show higher plate efficiencies than identical columns driven by pressure, and (4) that 100,000 plate HPLC separations can be achieved in relatively short times of 30 minutes using in situ derivatised drawn packed capillaries containing 3 and 5 μm ODS-silica gels.