Affinity chromatography is a technique used to separate biochemical compounds based on a reversible interaction between a compound and a ligand coupled to a chromatography matrix. It offers selectivity and can purify compounds that may be difficult to separate by other techniques. Key aspects of affinity chromatography include the matrix, ligand, ligand immobilization through various coupling methods, and elution techniques to reverse binding. Biomimetic dyes designed to mimic natural ligands can function as ligands in affinity chromatography.