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Department of Chemistry

SEC

Service Manager: Dr. Lian Hutchings

Size Exclusion Chromatography (SEC)

SEC is a liquid chromatography technique in which molecules are separated by molecular size in solution (hydrodynamic volume). It is used predominantly for the molecular weight analysis of polymers.  There are currently two triple detection SEC instruments available for molecular weight analysis 

  • A Viscotek TDA 302 complete with a GPCmax autosampler. This set up runs permanently with THF as the mobile phase.
  • A Viscotek TDA 302 which runs with polar solvents such as DMF or DMAc.

There is some flexibility in what solvents we use on the two systems and the eluent can be changed should the demand justify it. The so-called Triple Detector SEC3 system includes a four-capillary differential viscometer, right-angle laser light scattering detector (RALLS), and differential refractometer. This enables us to obtain molecular weight, molecular size, intrinsic viscosity and branching information using the modular WindowsTM-based TriSEC software. The combination of three detectors provides the choice of three different techniques (triple detection, universal calibration or conventional calibration), so that the appropriate SEC technique can be employed for a specific application or user requirement.

Triple detection uses light scattering to determine molecular weight. Light scattering, however, has limitations and cannot be used for samples of low molecular weight, poor dn/dc or varying dn/dc. In these cases Conventional and Universal Calibration applications are also available. Both systems have colour graphic and reporting capabilities.

Temperature Gradient Interaction Chromatography (TGIC)

TGIC is a liquid chromatography technique in which polmer molecules are separated by the magnitude of the interacton between the polymer chains and the stationary phase. As such polymers are separated by their molecular weight or chemical structure rather than hydrodynamic volume. This technique - originally develped by Professor Taihyun Chang at POSTECH University in South Korea - is increasingly being used alongside the more traditional SEC, especially in the characterisation of branched polymers. Although this technique is not offered as a service in Durham at present, we would be happy to discuss potential collaborations.

Contact Details

Dr Pamela Robinson
Analytical Services Coordinator
+44 (0)191 334 4646
analytical.services@durham.ac.uk