How does affinity purification work?

Affinity purification or affinity chromatography makes use of differences in binding interactions between biomolecules in the stationary and mobile phases. 

In this process, a select ligand is chemically immobilized or bound to a solid support or column. When a complex mixture is passed over the support column, the molecules that have a specific binding affinity to that particular ligand will interact with the ligand and become bound. The unbound molecules in the sample are then eluted and the bound molecule is stripped away from the support column, resulting in its purification from the original sample.