Isotachophoresis: analysis and computation of the structure of the ionic species interface

• Published in: Journal of Chromatography A 1987, Vol.405, p.77-85
• Main Authors: Su, Y., Palusinski, O.A., Fife, P.C.
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts: preparations and properties; Catalytic reactions; Chemistry; Exact sciences and technology; General and physical chemistry; General. Nomenclature, chemical documentation, computer chemistry; Theory of reactions, general kinetics; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0021-9673
• DOI: 10.1016/S0021-9673(01)81749-0

In the steady state of isotachophoresis the separated species form the zones migrating with constant velocity. This paper addresses the problem of computing the concentration of species in a transition region between two adjacent zones. The computation is complicated by the presence of a small parameter, ε, entering into Poisson's equation. Usual simplification consists of treating this parameter as negligibly small and thus reducing the Poisson equation to an algebraic electroneutrality relation between the concentrations of relevant species. However, the accuracy of such simplification has not been studied in the literature. Here we describe a numerical technique for computing the concentration profiles in a transition region either with or without the electroneutrality assumption. The method is based on an existence—uniqueness theory for the problem developed by the authors. Examples of numerical results computed for selected isotachophoresis systems are given.