Binary diffusion coefficients and retention factors for polar compounds in supercritical carbon dioxide by chromatographic impulse response method

The chromatographic impulse response (CIR) method with curve fitting was employed for measuring binary diffusion coefficients D12 at infinite dilution for polar compounds such as benzoic acid and C1 to C3 mono-alcohols in supercritical (SC) carbon dioxide at 313.2 K and pressures higher than 9.5 MPa. The measured D12 values for the polar compounds were expressed with two correlations which well represent binary diffusion coefficients for non-polar and weak polar compounds, i.e. the correlation of D12/T as a function of CO2 viscosity and the Schmidt number correlation. Moreover, the slope was −0.5 in logarithmic plot of D12 versus solute molecular weight over the range of molecular weight from 32 to 1138 at 313.2 K and 11.0 MPa.