Size‐Exclusion Chromatography of Polymers

Abstract

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

Toward a More General Solution to the Band-Broadening Problem in Size Separation of Polymers

“…Techniques for characterizing polymers by their size in dilute solution include size-exclusion chromatography (SEC), temperature-gradient interaction chromatography, anionic and cationic-exchange chromatography, capillary electrophoresis and the various types of field-flow fractionation . The separation principle has been shown for SEC − to be through the hydrodynamic volume V h .…”

Analysis of High Molar Mass Branched Polybutadienes by SEC-MALLS and AF4-MALLS

“…The characterization of complex polymeric materials requires accurate analytical techniques that address the various parameters of molecular heterogeneity. Among them, size exclusion chromatography (SEC) is the most prominent method for the analysis of molar mass distributions (MMD). − SEC coupled to a concentration detector such as a refractive index (RI) or ultraviolet (UV) detectors together with well-characterized calibration standards (e.g., polystyrene) are commonly used for the determination of relative molar mass values. These are then termed apparent molar masses or e.g.…”

Development and validation of an HPLC method for the determination of hyaluronic acid active substance in pharmaceutical formulations

“…One of the biggest disadvantages of derivatization is the lack of stability. The reaction products are unstable and probably have short half-lives due to spontaneous intermolecular rearrangement [9,10].…”