Two-phase flow is investigated in the context of liquid chromatography. In order to describe the column behavior in the presence of multiple convective phases, an equilibrium theory model is established, accounting for both adsorption and multiphase flow. The validity of this model is studied specifically for the experimental system phenetole-methanol-water on a Zorbax 300SB-C18 column. For this purpose, the experimental system is characterized in terms of thermodynamic liquid-liquid equilibria, adsorption behavior, and hydrodynamic properties by independent experimental campaigns. Mathematical relationships are established, describing the investigated effects. Implementation of these relationships in the equilibrium theory model and application of the model to calculate elution profiles provides a quantitative description of experimental data from dynamic column experiments. The good agreement validates the model, its assumptions, and the established relationships. This study provides a thorough insight on the implications of multiple convective phases in the context of liquid chromatography.