gelpermeatio

Gelpermeatio, in Dutch, refers to gel permeation chromatography (GPC), a form of size-exclusion chromatography used to characterize polymers by molecular weight distribution. In GPC, a solution of polymer is injected into a column packed with porous beads. The separation occurs because molecules diffuse into pores: large molecules access fewer pores and move through the column more quickly, while small molecules access more pores and elute later. The eluent is detected, commonly with refractive index detectors, UV detectors, or light-scattering detectors. When combined with multi-angle light scattering (MALS) or viscometry, GPC provides information about molecular weight and intrinsic viscosity in addition to distribution.

Calibration uses polymer standards of known molecular weight, typically polystyrene or PMMA, in the same solvent and at the same temperature. The elution volume of a sample is related to its hydrodynamic volume; conversion to molecular weight requires a calibration curve. Results depend on chemical structure and conformation; different polymers in different solvents can yield different apparent molecular weights.

Applications include determination of molecular weight averages Mn and Mw and the polydispersity index Mw/Mn, assessment of polymerization efficiency, quality control, and studying molecular weight distribution and branching. Advances combine GPC with light scattering to obtain absolute molecular weights, independent of calibration standards.

Limitations include sensitivity to solvent quality, sample solubility, and column aging; non-ideal interactions between polymer and column; using inappropriate standards can bias Mw values. Proper method validation and reporting of conditions (solvent, temperature, column set, detector, and calibration) are essential.