Effect of ion species on change in particle electrophoresis caused by change in applied electric field

• Published in: Colloid and interface science communications 2021-07, Vol.43, p.100462, Article 100462
• Main Authors: Fukasawa, Tomonori, Maruyama, Naoki, Ono, Kosei, Ishigami, Toru, Fukui, Kunihiro
• Format: Article
• Language: English
• Subjects: Electric field; Electrolyte concentration; Electrophoresis; Electrophoretic mobility; Hofmeister effect; Ion hydration; Particle size; Polystyrene latex particle; Steric effect; Zeta potential
• ISSN: 2215-0382; 2215-0382
• DOI: 10.1016/j.colcom.2021.100462

The effects of ion species (Li+, Na+, NH4+, Cs+, guanidinium (Gdm+), and tetraphenylarsonium (Ph4As+)) and applied electric fields on the electrophoretic mobility of hydrophobic sulfate polystyrene latex particles were experimentally investigated via direct measurements based on microscopic electrophoresis. At a high electrolyte concentration (50 mM), as the applied electric field increased, the electrophoretic mobility increased and the fraction of charge in the slipping layer (FOC) decreased, before converging to certain constant values for each cation; thus, the ion accumulation was weak, and the amount of cations in the slipping layer decreased as the applied electric field increased. Furthermore, FOC was smaller for cations with higher hydrophilicity, indicating that higher-hydration ions are less likely to accumulate in the slipping layer. These results can be useful for evaluating the ion-accumulation state around particles based on electrophoretic mobility measurements wherein the applied electric field is controlled as an operational parameter. [Display omitted] •The effect of applied electric field on electrophoretic mobility is investigated.•Electrophoretic mobility increases with applied electric field.•The amount of ions in the slipping layer decreases with increasing electric field.•Higher-hydration ions are less likely to accumulate in the slipping layer.•The obtained results will help in evaluating the state of ion accumulation.