Displacement and Dispersion of Particles of Finite Size in Flow Channels with Lateral Forces. Field-Flow Fractionation and Hydrodynamic Chromatography

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Abstract
The role of finite particle size is established for two flow-channel separation techniques: hydrodynamic Chromatography (HC) and field-flow fractionation (FFF). Both mean displacement velocity and dispersion are affected. A model is established where, for simple channel symmetries, the influence of particle size is calculated in terms of modifications of the known FFF equations for infinitely small particles displaced in a narrow channel and subject to lateral forces. This approach avoids the tedium of obtaining new solutions to the basic mass-transport equations, and the results automatically relate to those at the zero-size limit. Specific equations are derived for channels between infinite parallel walls. The retention ratio is treated first; this parameter yields the mean displacement velocity. The plate height, which is treated subsequently, yields effective axial dispersion. Plots of the relevant equations are given and some implications and complications in the theory of HC and FFF are noted.