Size-Exclusion Chromatography of Polymers

摘要: Size-exclusion chromatography (SEC) is a standard technique for determining molar mass averages and distributions (MMDs) of polymers. Sometimes the termsgel permeation (GPC) or gel filtration (GFC) are also used, but SEC should be preferred, because this term describes mechanism much better: polymer molecules separated according to their hydrodynamic volumes (which can correlated with mass), larger size exiting first followed by smaller. Molar masses determined either from calibration using sensitive detectors. In case copolymers, knowledge chemical composition along MMD required, which obtained combinations different concentration As polymers typically somewhat different, will eluted in same slice chromatogram. Obviously, discrimination between such requires two-dimensional separation, one dimension may SEC, other chromatographic technique, separates rather than mass, as liquid adsorption (LAC), at critical point (often called under conditions, LCCC), supercritical fluid (SFC), temperature rising elution fractionation (TREF), etc. In lower range, spectroscopy competes SEC. The most frequently used matrix-assisted laser desorption/ionization time-of-flight (MALDI/TOF/MS), cannot, however, provide quantitatively accurate MMDs. Due its excellent resolution it combined techniques order increase reliability analysis.