Particle loaded monolithic sol-gel columns for capillary electrochromatography: A new dimension for high performance liquid chromatography

Particle-loaded (3 mu m, octadecylsilica) monolithic sol-gel columns have b een prepared and selected characteristics measured. Several electrical prop erties may be calculated from simple current measurements in the column as a whole. Resistivity in the packed segment is approximately three times tha t in open segments, resulting in a 60% increase in field strength in the pa cked regions compared to the capillary with no packing. The surprisingly hi gh specific permeability of these sol-gel columns is characteristic of 8-mu m particles, which allows their operation in the microLC mode at pressures as low as 69 kPa where their efficiency is about 50,000 plates per meter a nd in the CEC mode a here efficiency is about 106,000 plates per meter at 5 kV.There is a relatively rapid loss of efficiency with increasing linear v elocity beyond 0.2 mm/s in microLC mode, which may be due to additional dif fusion processes in the inter-particulate voids. A rapid loss of efficiency above 0.5 mm/s is also observed in the CEC mode, for the same reasons. Chr omatographic retention behavior in either separation mode is characteristic of conventional octadecylsilica particles, indicating that analytes have s ignificant access to the surface within the pores of the immobilized bonded phase.