Binary diffusion coefficients D-12 and retention factors k for dibenzo-24-crown-8 and 15-crown-5 ethers at 308.18 and 313.20 K, and vitamin K-1 at 313.20 K were measured in supercritical carbon dioxide by the chromatographic impulse response technique, and the effects of molecular shapes on the D-12 values were studied. At 313.2 K and 11.0 MPa the D-12 value of 15-crown-5 was higher than that predicted from the D-12 correlation with molecular weight MW over the range from 32 of methanol to 1138 of trinervonin reported in our previous studies, while the D-12 value of dibenzo-24-crown-8. disk shape molecule with MW=448.5, was almost in agreement with that of vitamin K-1, long chain molecule with MW=450.7, and with those predicted from the correlation. (c) 2007 Elsevier B.V. All rights reserved.