GelPermeationsChromatographie

Gel permeation chromatography (GPC), also known as size-exclusion chromatography (SEC) when used for polymers, is an analytical technique that separates molecules by their effective size in solution. In GPC, a polymer solution is passed through a column packed with porous polymer beads. Large molecules cannot enter many of the pores and thus elute first, while smaller molecules penetrate more pores and elute later. The separation is based on hydrodynamic volume rather than chemical interactions.

Typical GPC systems include a solvent delivery pump, an autosampler, one or more calibrated columns, a temperature-controlled oven, and a detector. The choice of solvent depends on the polymer and may be tetrahydrofuran, dimethylformamide, or other compatible media. Detectors commonly used are refractive index, with additional detectors such as UV, light scattering, or viscometry providing more information about molecular weight and conformation.

Data produced by GPC are related to molecular weight distribution. Primary outputs include the number-average molecular weight (Mn), weight-average molecular weight (Mw), and the polydispersity index (PDI = Mw/Mn). Calibration is typically performed with polymer standards of known molecular weights, often polystyrene or PMMA, to relate elution volume to molecular weight for the sample class. Absolute molecular weights can be obtained with multi-angle light scattering or intrinsic viscosity detectors.

Applications span polymer characterization, quality control, and research in materials science. Limitations include dependence on solvent compatibility, potential interactions with the column, and the assumption that molecular size correlates with elution behavior similarly across different polymers.