Size exclusion chromatography, (SEC) is a chromatographic method commonly used to separate large molecules or macromolecular complexes such as proteins and industrial polymers. It operates on the principle of separation of components according to their size or hydrodynamic volume. Particles of differing size will elute through the column’s stationary phase at varying rates.
SEC can be used as a measure of both the size and the polydispersity of a synthesized polymer - i.e. the distribution of polymer molecules of varying size. If standards of a known size are analyzed previously, a calibration curve can be created to determine the sizes of polymer molecules of interest. Alternatively, techniques such as light scattering and/or viscometry can be used online with SEC to yield approximate molecular weights without reliance on calibration with standards of known molecular weight. However, these techniques are not particularly accurate and, to complicate matters further, two polymers can have the same molecular weight but differing structures - this added complication can be investigated using mass spectrometry.