Gel permeation chromatography

Lore & Background

Gel permeation chromatography separates analytes based on their size or hydrodynamic volume, unlike other chromatographic techniques that depend on chemical or physical interactions. Separation occurs via porous gel beads packed inside a column; larger molecules are excluded from pores and elute earlier, while smaller molecules enter pores and elute later. The process takes place without any interaction of the analytes with the surface of the stationary phase. Each column has a range of molecular weights that can be separated according to pore sizes, and for broad molecular weight ranges, several columns with varying pore volumes may be used in tandem.

Reader's Guide

Gel permeation chromatography is significant as the most widely used technique for analyzing polymer samples to determine molecular weights and weight distributions. It allows determination of dispersity (Đ) and viscosity molecular weight (Mv), and based on other data, number average (Mn), weight average (Mw), and size average (Mz) molecular weights can be determined. The technique is conducted in chromatography systems similar to high performance liquid chromatography, using organic solvents as eluents. Common detectors include differential refractometers and UV photometers. GPC systems and consumables are available from multiple manufacturers, and the technique is essential both for analyzing polymers and purifying desired products.

Did You Know?

• GPC separates analytes based on size or hydrodynamic volume, not chemical interactions.
• Polystyrene standards with dispersities less than 1.2 are typically used to calibrate GPC.
• The total column volume is given by Vt = Vg + Vi + Vo, where Vg is gel volume, Vi is pore volume, and Vo is void volume.