Analytical Sciences

Measurements of Binary Diffusion Coefficients, Retention Factors and Partial Molar Volumes for Myristoleic Acid and Its Methyl Ester in Supercritical Carbon Dioxide

Chang Yi KONG,* Masakazu MORI,* Toshitaka FUNAZUKURI,** and Seiichiro KAGEI*

*Faculty of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya, Yokohama 240-8501, Japan
**Department of Applied Chemistry, Institute of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo, Tokyo 112-8551, Japan

The binary diffusion coefficients, D₁₂, and retention factors for myristoleic acid and its methyl ester at infinite dilution were measured by the chromatographic impulse response technique in supercritical carbon dioxide at temperatures of 313.2, 333.2 and 343.2 K and pressures from 9.2 to 30 MPa for the acid, and from 8.0 to 14 MPa for the ester. Although the D₁₂ values were represented by the two correlations, the D₁₂/T vs. CO₂ viscosity and the Schmidt-number correlations, which are valid for more than 40 compounds that we have measured so far, significant temperature dependences were observed for the ester. Moreover, the D₁₂ values for the ester at 313.2 K downward deviated from the background values around 400 kg m^-3, where the partial molar volumes, obtained from the correlation between the retention factors measured and CO₂ densities, showed large negative values.

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