GPC is used to measure various properties of large molecules, allowing researchers to characterize molecules such as synthetic polymers and natural polymers such as polysaccharides.
When coupled with light scattering, viscometer and concentration detectors (RI, UV), GPC can measure absolute molecular weight, molecular size and intrinsic viscosity, and generate information on macromolecular structure, conformation, aggregation and branching.
How it works – GPC is a size-exclusion liquid chromatographic technique that separates dissolved macromolecules according to their sizes. The sample solution is introduced into the column, which is filled with rigid-structure, porous particles, and is carried by solvent (mobile phase) through the column. The size separation takes place by repeated exchange of the solute molecules between the bulk solvent of the mobile phase and the stationary liquid phase within the pores of the particles. The pore size of the particles determines the molecular size range within which separation occurs.
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Instrumentation Available
Key Attributes
- The GPC system has the following components:
- 1. Pump – delivers the polymer in solution through the system;
- 2. Injector – introduces the polymer solution into the mobile phase;
- 3. Column Set – efficiently separates sample components from one another;
- 4. Detector (RI, UV, light scattering, viscometer) – monitors the separation and responds to components as they elute from the column;
- 5. Automatic data processing equipment (Empower, OmniSEC software packages)- automatically calculates, records, and reports numerical values for Mn, Mw, Mz, Mp, and PDI. Data systems can also provide complete control of GPC systems so that large numbers of samples can be run unattended and raw data can be automatically processed.
- Temperature operation: ambient – 220 °C.
- Calibration standards: organic and aqueous.
Strengths
- Solvents variety ranging from aqueous to non-polar organic solvents;
- Separating polymers with molecular weighs from a few hundred to several millions of Daltons;
- Multiple detectors (refractive index, ultraviolet, light scattering, online-viscometer);
- Temperature analysis ranges from ambient to 220°C;
- Characterize polymers and separate mixtures into discrete fractions, such as polymer, oligomer, and any non-polymeric additives.
Limitations
- Sample preparation (solubility, concentration, volume, sample – column packing material interaction, sample filtration);
- Solvent effects (solvent viscosity, boiling point, solvent-column packing material interaction);
- Column selection (solvent type, pore size, number of column in the set, price per column);
- Limited number (type) of GPC standards.
Applications
- Molecular weights (Mn, Mw, Mz, Mp) and molecular weight distribution (PDI);
- Analysis of branching and chain folding;
- Analysis of copolymers;
- Analysis of polymer and additives blending;
- Quality assurance and quality control.
Additional Reading
