Multi-Detector GPC/SEC Analysis of Polysaccharides

Polysaccharides are abundant, biological polymers composed of monosaccharides, or sugars. As a diverse class of naturally-occurring materials, polysaccharides have been used in applications ranging from paper and cotton manufacturing, to bioprinting and bioengineering, to pharmaceuticals, gelling agents in food, and other consumer products. In order to produce these items, manufacturers and researchers have to be able to isolate and identify polysaccharides with particular molecular properties, such as molecular weight, intrinsic viscosity, and molecular size, that are appropriate for each specific application. As such, the accurate analysis and molecular weight characterization of polysaccharides is critical.

Gel permeation chromatography (GPC) or, equivalently, size-exclusion chromatography (SEC), is a widely used technique to characterize a range of macromolecules, from bulk manufactured materials to natural polymers and proteins. This technique can be used to measure the molecular weight moments (Mw, Mn), dispersity (Mw/Mn), intrinsic viscosity (IV) and hydrodynamic radius (RH) of these macromolecules. Figure 1 shows a complete setup of Malvern’s OMNISEC GPC/SEC system.

A brief overview of how GPC/SEC works: a solvated sample is carried by a liquid mobile phase through an analytical column full of porous gel particles, where diffusion-controlled separation of the macromolecular components occurs and is ultimately observed by different detectors as each slice of sample elutes. The samples elute based on molecular size, with the larger molecules eluting first. It is important to remember that the elution order is based on molecular size and not molecular weight. A common advanced detection GPC/SEC setup includes refractive index (RI), viscometer, light scattering detectors, and sometimes a UV/ Vis photodiode array detector.

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