Perfusive Electroosmotic Transport in Packed Capillary Electrochromatography: Mechanism and Utility

Ž Abstract: In this study, silica-based packing materials with pore sizes herein ̊ . referred to primarily as channel diameters, d ranging from 60 to 4000 A were ch utilized to elucidate the role of pore size in CEC. Separations were conducted using a commercially available CE system, the inlet and outlet buffer reservoir compartments having been modified to allow constant application of ;150 psi of helium head pressure. This application of pressure was sufficient to prevent nucleation of gas bubbles, a common practical hindrance in CEC. On-column UV detection was performed following the outlet frit of the packed section of the capillary. Electrokinetic sample introduction was employed. The experimental results of these studies indicate that the use of wide-pore media in CEC may provide for notable increases in efficiency. When wide-channel, corpuscular silica packing materials are employed in CEC, the microbeads which comprise the larger particle begin to dictate the ‘‘true’’ or effective diameter of the packing particles, and analytes experience two distinct regions of pore space through which eluent Ž . flows: the intraparticle region inside the particles of packing material and the Ž . interparticle region between adjacent particles of packing material . The percent of total pore volume contributed by through-pores is likely to be relatively small in the packing materials used, suggesting that particles with a greater degree of perfusive character could provide even further increases in both efficiency and loading capacity. These larger diameter packing materials are easier to work with, less expensive, and offer increased probability of success in the manufacture of packed capillaries for CEC. Q 1997 John Wiley & Sons, Inc. J Micro Sep 9: 389]397, 1997