Gel filtration chromatography, also known as size-exclusion chromatography, uses porous gel media to separate substances according to molecular size. Large molecules cannot enter the gel pores and elute rapidly, while small molecules can penetrate into the pores, reside longer, and elute more slowly. It employs mild separation conditions that preserve biological activity, making it widely used in the purification of recombinant proteins and antibodies. It is also applied for sample desalting, buffer exchange, and preliminary molecular weight analysis.