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Free keywords:
adsorption; capillary electrochromatography; coupled transports; electrical double layer; electroosmosis; electrophoresis; nonlinear effects
Abstract:
A mathematical modelling approach for open-tubular capillary electrochromatography is presented. The spatially one- dimensional model takes into account (i) a coupling of (non)linear adsorption of positively or negatively charged analyte molecules (at a negatively charged capillary inner surface) with the equilibrium electrokinetics at this solid- liquid interface, (ii) mobile phase transport by electroosmosis and pressure-driven flow, as well as (iii) transport of species by electrophoresis and molecular diffusion. Under these conditions the local zeta-potential and electroosmotic mobility become a function of the concentration of the charged analyte. The resulting inhomogeneity of electroosmotic flow through the capillary produces a compensating pore pressure as requirement for incompressible mobile phase flow (i.e., for constant volumetric flow along the capillary). The results of the simulations are discussed in view of the surface-to-volume ratio of the capillary lumen, the analyte concentration (in combination with a Langmuir isotherm for the adsorption process), and buffer effects.
© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [accessed 2013 November 28th]
