Compressed carbon dioxide, doped with secondary and tertiary amine entrainers, was used for the separation of acetic and lactic acid. The solubility of the amines in liquid and supercritical CO2 was tested, and the partition of the acids between the aqueous and the amine-loaded gas phase was investigated. A model for the description of the phase equilibria based on the acid loading of the amine in the carbon dioxide phase was used. By performing semi-batch experiments, the rate-determining step of the separation was found to be the interphase reaction. The applicability of this separation process was tested and found to be feasible in a continuously operated countercurrent lab-scale extraction plant