Electrophoresis of a charge-regulated zwitterionic particle: influence of temperature and bulk salt concentration.

The influence of temperature on the electrophoretic behavior of a charge-regulated zwitterionic particle is investigated by considering a spherical SiO(2) particle in a relatively dilute aqueous NaCl solution of concentration C(NaCl) with its pH adjusted by NaOH and HCl as an example. A complete mobility-pH-temperature plot and a mobility-C(NaCl)-temperature plot are prepared for pH, C(NaCl), and temperature ranging from 3 to 9.5, 10(-4) to 10(-2) M, and 293 to 308 K, respectively, for the first time, and empirical correlation relationships are developed. These provide necessary information for both interpreting experimental data and designing electrophoresis devices, where the variation in the temperature can be a factor. In general, the absolute value of the particle mobility increases with T, and that value has a local maximum as pH varies.