Figure 1.

Schematic representation of the Elution-Extrusion CCC method using the velocity approach (see text). A – The elution period (Stage I). The mobile phase moves with a u_M linear velocity. B – The extrusion period starts. During the following Stage II, i.e, the sweeping elution, the solvent front moves with the mobile phase linear velocity u_M. At the column head, the “stationary” phase moves at the linear velocity u_S. At the same time, the “stationary” phase is really stationary only at those positions ahead of the solvent front. C – During the sweep elution time, the solutes located near the column end are still exposed to elution conditions, partitioning between the two phases as long as they are not passed by the “stationary’ phase solvent front. Only mobile phase exits the column. D – Extrusion (Stage III). The whole column contains only “stationary” phase, and all remaining solutes move at the S phase velocity, u_S. The peak marked with the infinite sign locates the position of carotene, a solute with a very high K_D constant that marks the end of the experiment when leaving the CCC column.