| Abstract
| - Solute dispersion in open-channel liquid chromatographyis often dominated by transverse diffusion limitations inthe mobile phase (Martin, M.; Guiochon, G. Anal. Chem.1984, 56, 614−620) convecting the solute species. Whilesuch dispersion is known to scale with the square of thePeclet number based on the narrower dimension of theconduit, the proportionality constant may significantly varywith the aspect ratio of the channel geometry. In thisarticle, we investigate the effect of channel sidewalls onaxial dispersion in electrokinetically and pressure-drivenchromatographic systems. The analysis presented hereclearly identifies the contribution from flow, wall retention,and the interaction between the two to the overall slugdispersion in the mobile phase for any arbitrary channelgeometry. The particular geometries that have beeninvestigated in this work, however, are the rectangular andthe isotropically etched profiles often employed in microanalysis systems. Further, the effectiveness of simpledouble-etched profiles proposed elsewhere (Dutta, D.;Leighton, D. T. Anal. Chem.2001, 73, 504−513) todiminish the effect of channel sidewalls on Taylor−Arisdispersion has also been examined. Analysis shows thatdispersion arising due to shear and wall retention, as wellas the interaction between the two, may be significantlyreduced in large aspect ratio microchannels for optimizedchannel geometries.
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