How does it work?

A GPC column is filled with porous beads through which molecules can diffuse. Large molecules only fit into the larger pores, and so travel through the column relatively quickly. Smaller molecules travel more slowly as they move through a greater number of pores, resulting in a separation based on molecular size. After this separation, species are monitored by differences in refractive index, viscosity, or by light scattering or fluorescence detectors.

In conventional GPC, standards of known molecular weight are used for calibration, and molecular weight averages and polydispersity of unknown samples can be measured relative to these. Multi-detector techniques can be used for more accurate molecular weight determination.