A conventional method was used to measure the melting points of the natural lipid tripalmitin and of the coenzyme ubiquinone (coQ 10) under high pressure carbon dioxide. The pressure-temperature behavior of the binary three-phase solid-liquid-gas (SLG) equilibrium for these and other systems, namely naphthalene and biphenyl with carbon dioxide, ethylene and ethane, were investigated using the Peng-Robinson equation of state (PR-EoS) with the van der Waals one fluid (vdw-1) mixing rules and with the NRTL equation to calculate the solute activity in the liquid phase. When the interaction parameter in the vdw-1 mixing rules could be determined by the PR-EoS through the correlation of the solid-fluid phase equilibrium data, the two NRTL parameters were used as adjustable parameters. The results showed that fairly good correlations could be achieved for the experimental pressure-temperature data of all the asymmetric systems studied here, indicating that the NRTL parameters are crucial for describing the pressure-temperature behavior but have little effect on the phase compositions at the SLG equilibrium. (c) 2005 Elsevier B.V. All rights reserved.