Binary diffusion coefficients, D-12, of the metal acetylacetonates, palladium(II) acetylacetonate and cobalt(III)acetylacetonate, were measured from 308.2 to 343.2 K over the pressure range from 9 to 40 MPa at infinite dilution in supercritical carbon dioxide using the chromatographic impulse response method. The effects of pressure, temperature, density, and viscosity on D-12 values were examined. It was observed that the D-12 values of palladium(II)acetylacetonate and cobalt(III)acetylacetonate were larger than those of lipids with similar molecular weights, such as arachidonic acid and monoolein, respectively. Furthermore, the measured D-12 data of each metal acetylacetonate were well correlated by the hydrodynamic equation D-12/T as a function of carbon dioxide viscosity. (C) 2010 Elsevier B.V. All rights reserved.