Size-exclusion chromatography (SEC), also known as molecular sieve chromatography,[1] is a chromatographic method in which molecules in solution are separated by their size, and in some cases molecular weight.[2] It is usually applied to large molecules or macromolecular complexes such as proteins and industrial polymers. Typically, when an aqueous solution is used to transport the sample through the column, the technique is known as gel-filtration chromatography, versus the name gel permeation chromatography, which is used when an organic solvent is used as a mobile phase.