What are the main types of chromatography used in downstream processing?

Major chromatography types include: Ion Exchange Chromatography (IEX) separating proteins by charge using anion (Q, DEAE) or cation (S, CM) exchangers; Affinity Chromatography using specific ligands (Protein A for antibodies, IMAC for His-tagged proteins); Size Exclusion Chromatography (SEC) separating by molecular size for polishing and buffer exchange; Hydrophobic Interaction Chromatography (HIC) separating by hydrophobicity; and Mixed-mode chromatography combining multiple interactions. Selection depends on protein properties, required purity, and scale. A typical platform process for antibodies uses Protein A capture, followed by IEX and/or HIC polishing steps.