Countercurrent chromatography: separation principle, mechanical design, development trends, and applications

Countercurrent chromatography (CCC) is the separation technique based on the different partition coefficients of the sample between two immiscible solvents, which is a liquid-liquid partition without solid support in the column. In this paper, Firstly, the mechanic’s equilibrium principle of CCC is described, which includes hydrostatic equilibrium system (HSES), hydrodynamic equilibrium system (HDES), unidirectional hydrodynamic equilibrium phenomenon, etc. The separation principle of the CCC is also explained. Secondly, the mechanical structure and design of parallel-axis CCC, cross-axis CCC, oblique-axis CCC, as well as some CCC derived from the three are illustrated respectively. Finally, the existing problems for the development of CCC have been exposed, and the trend of the future development direction and applications of CCC are discussed.