Property Calculation and Prediction for Selecting Solvent Systems in CCC

Abstract

A theoretical method is presented for the property calculation and prediction in selecting solvent systems of countercurrent chromatography (CCC). A Universal Functional‐group Activity Coefficients (UNIFAC) model is used as the solution model to describe the non‐ideality of the liquid mixtures. The results are as follows.

1.	Thermodynamic criterion is given to judge the possibility of phase split.
2.	If the phase split takes place, calculation of phase composition is carried out.
3.	Calculate the volume ratio of the two immiscible phases in the system.
4.	Densities are calculated without considering the volumetric non‐ideality.
5.	Viscosities are estimated by using the “cubic root summation.”
6.	Dielectric constants are obtained by using a semi‐empirical mixing rule.
7.	Interfacial tension is also estimated by another semi‐empirical equation.

Compared with experimental data, the calculation results are satisfactory and accurate. A program is written for the computer calculation. Only the volume ratio of the solvents is needed for the input of the computation. A chosen system can be examined in a few minutes. If mobile phase (stationary as well) is wanted in the separation practice, there is no need to “equilibrate” the solvents, just “prepare” this phase of any desired quantity according to the result of calculation.

Keywords:

• Solvent selection
• Countercurrent chromatography
• Modified UNIFAC model

Acknowledgment

This work was supported by the China Natural Sciences Foundation. The authors express their thanks to Dr. Y. Ito and Prof. T. Zhang for their encouragements. Mr. J. Huang gave some help in program improvement.