We discuss the effect of electrolytes on retention of aqueous colloidal polystyrene particles in asymmetrical flow (AF‐FFF) and thermal field‐flow fractionation (ThFFF). In both FFF subtechniques, interparticle interaction leads to non‐ideal fractionation behavior, which can result in a sample load dependency. Electrostatic repulsion is reduced with increasing electrolyte concentration, resulting in a pronounced increase of retention. At higher salinities, hydrophobic interactions dominate, thus applications of AF‐FFF under physiological conditions are limited. In ThFFF, also the separation mechanism of thermophoresis is affected by ionic shielding and experimental data are in accordance with recent theoretical models of thermophoresis.
Particle characterization by asymmetrical flow field‐flow fractionation (AF‐FFF) and thermal field‐flow fractionation (ThFFF) in aqueous solution is highly affected by the electrolyte in the carrier liquid. In this feature article, the impact of salinity and ion specificity on fractionation behavior is discussed. Forces acting in the fractionation channel and electrostatic particle–particle and particle–wall forces are highlighted.
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