The distribution constants (K-D,K-CO2) of 8-quinolinol derivatives (HA) between supercritical carbon dioxide (SC-CO2) and water were determined at 45 degrees C. The values of K-D,K-CO2 increased with an increase in the SC-CO2 pressure, that is, the SC-CO2 density (rho(CO2)). The values of K-D,K-CO2 were evaluated by a comparison of the distribution constant (K-D,K-org) of HA between heptane and water. Based on a linear relationship between log K-D,K-org and log KD-CO2. it was suggested that the interaction of heptane molecules with HA is similar to that of CO2 molecules. The solvent effect on the distribution behaviors of HA between SC-CO2 and water was evaluated based on a regular solution theory. The solubility parameters of HA in the SC-CO2-water extraction system are smaller than those in the organic solvent-water extraction system, suggesting that the interaction between HA and CO2 molecules, such as the dispersion force, dipole-dipole and dipole-induced dipole interactions, is weaker than that between HA and the organic solvent molecules. (C) 2009 Elsevier B.V. All rights reserved.