title: On the ionic strength dependence of the electrophoretic mobility: From 2D to 3D slope-plots.
abstract: Determining the charge and the nature (small ion, nanoparticle, or polyelectrolyte) of an unknown solute from its electrophoretic characteristics remains a challenging issue. In this work, we demonstrate that, if the knowledge of the effective electrophoretic mobility (μep) at a given ionic strength is not sufficient to characterize a given solute, the combination of this parameter with (i) the relative decrease of the electrophoretic mobility with the ionic strength (S), and (ii) the hydrodynamic radius (Rh), is sufficient (in most cases) to deduce the nature of the solute and its charge. These three parameters are experimentally accessible by CZE and Taylor dispersion analysis performed on the same instrumentation. 3D representation of the three aforementioned parameters (μep; S and Rh) is proposed to visualize the differences in the electrophoretic behavior between solutes according to their charge and nature. Surprisingly, such 3D slope plot in the case of small ions and nanoparticles looks like a "whale-tail," while polyelectrolyte contour plot represents a rather simple and monotonous map that is independent of solute size. This work also sets how to estimate the effective charge of a solute from a given experimental (S,Rh,μ ep 5 mM ) triplet, which is not possible to obtain unambiguously with only (Rh,μ ep 5 mM ) or (S,μ ep 5 mM ) doublet, where μ ep 5 mM is the effective electrophoretic mobility at 5 mM ionic strength.
authors.affiliation: Institut des Biomolécules Max Mousseron, (UMR 5247 CNRS, Université de Montpellier, Ecole Nationale Supérieure de Chimie de Montpellier), Montpellier, France.
authors.forename: Hervé
authors.initials: H
authors.lastname: Cottet
authors.affiliation: Department of Chemistry, Georgia State University, Atlanta, Georgia, USA.
authors.forename: Hengfu
authors.initials: H
authors.lastname: Wu
authors.affiliation: Department of Chemistry, Georgia State University, Atlanta, Georgia, USA.
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Allison
mesh_terms: D019075:Electrophoresis, Capillary; D057446:Hydrodynamics; D008962:Models, Theoretical; D053758:Nanoparticles / Q000737:chemistry; D009994:Osmolar Concentration; D010316:Particle Size; D000071228:Polyelectrolytes / Q000737:chemistry
chemical_list: D000071228:Polyelectrolytes
keywords: Electrophoretic behavior; Electrophoretic mobility modeling; Nanoparticles; Polyelectrolytes; Small ions