Comparison of column packing techniques for capillary electrochromatography

Four different column packing techniques were used to pack capillary columns for comparison in capillary electrochromatography (CEC); the techniques were slurry pressure packing, using supercritical CO₂, electrokinetic packing, and packing with centripetal forces. Capillary columns of 50 μm ID were packed with each technique and evaluated under electrochromatographic conditions. An initial evaluation suggested that among the packing techniques, supercritical CO₂ packing and packing with centripetal forces produced the most efficient packed capillaries. However, examining the various protocols in detail revealed that experience of the practitioner and familiarity with packing equipment are critical factors in column fabrication. Upon further investigation of the packing techniques and optimization of the column fabrication protocol, columns packed by the four packing techniques showed similar performance when operated under CEC conditions. Efficiencies of 270,000-300,000 plates/m were observed for 50 μm ID capillary columns packed with 3 μm packing material.