After the entire sample is loaded, the feed is switched to the displacer, chosen to have higher affinity than any sample component.  The displacer forms a sharp-edged zone at the head of the column, pushing the other components downstream.  Each sample component now acts as a displacer for the lower-affinity solutes, and the solutes sort themselves out into a series of contiguous bands (a "displacement train"), all moving downstream at the rate set by the displacer.  The size and loading of the column are chosen to let this sorting process reach completion before the components reach the bottom of the column.  The solutes appear at the bottom of the column as a series of contiguous zones, each consisting of one purified component, with the concentration within each individual zone effectively uniform.