Practical approach to high-speed counter-current chromatography

Abstract

Counter-current chromatography (CCC0 is mainly used in the preparative separation, extraction and purification of samples. CCC does not operate with a solid stationary phase. Two immiscible liquid phases are used. One is the liquid mobile phase and the other is the liquid stationary phase. Centrifugal fields are used to retain the liquid stationary phase while the mobile phase is pushed through it. The CCC “column” if often a continuous open tube, coiled on a spool which is rotated in a centrifuge. Most high-speed counter-current chromatographs are scheme IV Ito coil planet centrifuges. A practical CCC approach is reported in this paper. The user-adjustable parameters are divided into (i) configuration parameters and (ii) operating parameters. The configuration parameters are the tube internal diameter, the spool radius, the number of turns and the total internal apparatus volume. The operating parameters are three active parameters (mobile phase flow-rate, spool rotation speed and temperature) and two passive parameters (the stationary phase retention percentage and the driving pressure). The choice of solvents to be used as the biphasic liquid systems is critical. Tie lines in ternary phase diagrams are used to optimize the solvent choice with hexane—methanol—water and the chloroform—methanol—water systems. The effects of interdependent parameters on the CCC chromatograms are discussed and illustrated with examples. It is shown that a highly efficient counter-current chromatograph can have a poor resolving power if it cannot retain a sufficient amount of liquid stationary phase.