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The size or hydrodynamic radius RH can be determined in two ways. The first method is by Dynamic Light Scattering (DLS), which is generally used as a batch technique to measure the average size in the whole sample, but can be used as a detector for Size Exclusion Chromatography (GPC/SEC).

A very accurate and precise method of obtaining RH of all components in a sample is by triple detection after separation by SEC.

By the use of online light scattering and viscometer detectors, the MW and intrinsic viscosity of the polymer or protein can be determined and hence the RH calculated at any point on the chromatogram.

The benefit of both these techniques is that there is no practical upper or lower size limit for the materials being investigated.

The measurement of molecular size is a useful parameter for a number of applications:

  • Comparison with molecular weight gives information about structure
  • DLS can use molecular size to give a quick estimate of molecular weight
  • DLS can give a fast screen of protein purity
  • Determination of protein melting point.

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Introducing the most advanced GPC/SEC system available: OMNISEC Technical Note (English)

Here we describe the features and benefits of the OMNISEC GPC/SEC system and explain how OMNISEC sets a new standard in molecular characterization.



Combined DLS/Raman provides New Molecular Insights of Complex Fluids Article (English)

In particular, this article demonstrates the correlation between molecular changes (Raman Spectroscopy) and microstructural evolution of rheological properties (DLS, DLS-optical microrheology) for the first time for surfactant-based wormlike micellar...



Size Exclusion Chromatography / Gel Permeation Chromatography: An Introduction in 30 Minutes Whitepaper (English)

GPC/SEC is mainly used for the characterization of macromolecules including synthetic and natural polymers (including polysaccharides) as well as proteins or RNA/DNA. This white paper provides an introduction to the technique in 30 minutes.



Overcoming challenges in the detection and characterization of PLGA using the latest developments in GPC/SEC technology Poster (English)

PLA, PLGA and their copolymers are biocompatible, biodegradable and used in a number of medical applications. However, analysis of this low molecular weight and low dn/dc sample pushes the sensitivity boundaries of all previous light scattering detec...


Keywords: Polymer solutions English Poster Molecular structure Molecular size Molecular weight Gel Permeation Chromatography Static Light Scattering Size Exclusion Chromatography OMNISEC 

Using GPC/SEC for excipient characterization Article (English)

The properties of polymeric excipients can directly affect the clinical efficacy, safety, and quality of a finished pharmaceutical product and are routinely identified as critical quality attributes (CQAs). This article looks at how gel permeation/si...


Keywords: English Article Molecular structure Molecular size Molecular weight Gel Permeation Chromatography Static Light Scattering Size Exclusion Chromatography Biological drug characterization and development Drug discovery Excipients and coatings OMNISEC 
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