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More precisely, it is the "gel permeation chromatography" that differentiates by molecular weight.
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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. SEC is a widely used polymer characterization method because of its ability to provide good molar mass distribution (Mw) results for polymers.

The main application of gel-filtration chromatography is the fractionation of proteins and other water-soluble polymers, while gel permeation chromatography is used to analyze the molecular weight distribution of organic-soluble polymers.

https://en.wikipedia.org/wiki/Size-exclusion_chromatography

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Proteins that differ in mass can be separated by gel filtration chromatography.
https://www.ncbi.nlm.nih.gov/books/NBK21589/
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medium will be liberated from high molecular weight components by gel filtration
https://books.google.com/books?id=kO_wCAAAQBAJ&pg=PA92&lpg=P...
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Gel filtration chromatography is a separation based on size. It is also called molecular exclusion or gel permeation chromatography. In gel filtration chromatography, the stationary phase consists of porous beads with a well-defined range of pore sizes.

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Gel Filtration/Size Exclusion Chromatography

Fractionation is used for the separation of macromolecules of different sizes. The fractionation range of the resin defines the range of molecular weights that should be separable. Typical applications of fractionation using SEC include preparative purification, analysis of aggregates and molecular weight determination of proteins, peptides, and nucleic acids.
http://www.gelifesciences.com/webapp/wcs/stores/servlet/Cate...