What is size-exclusion chromatography?

Size-exclusion chromatography (SEC), also known as gel filtration chromatography or molecular sieve chromatography, is a chromatographic method that separate molecules based on the molecular size, which is widely used in protein purification and polymer characterization.

A porous matrix is used as the stationary phase in SEC, to which the analytes have different degrees of access due to steric reasons. Large molecules are excluded from the matrix thus would be eluted first, whereas small molecules who are trapped by the pores will have greater access and would be eluted later. Analytes should have minimal or ideally no interaction with the surface of stationary phase, so that the separation is solely based on the difference in molecular size, rather than chemical or electrostatic interactions.