Coalescence is strongly affected by trace components. Studies suggest the usage of the Derjaguin-Landau-Verwey-Overbeek force in coalescence modeling. Thus, data regarding the electrostatic potential are needed. Determination of the partition coefficient of a charged dye dissolved in salt-containing two-phase systems allows to evaluate the electrostatic potential difference relative to a reference system by evaluation with the extended Albertsson model. The corresponding first settling tests show the strong effect of the relative electrostatic potential difference on the dispersion behavior.