Gel Filtration/ Size Exclusion

Size exclusion chromatography (SEC) or gel filtration is used to separate a wide range of molecules according to size, including proteins (enzymes), polysaccharides and nucleic acids. 

There are two major categories of SEC; Group separation and Fractionation.

In group separation, for example desalting, samples are separated into two major groups. For desalting select a resin that excludes the larger molecules from the pores of beads, whiles smaller molecules (salts) are retained in the pores.

Fractionation is used to separate macromolecules of different sizes. Here the fractionation range of the resin defines the range of molecular weights that can be separated. Applications that use fractionation by SEC include, preparative purification, analysis of aggregates and molecular weight determination of proteins and nucleic acids.