Gel permeation chromatography is a chromatographic technique commonly used in the analysis of macromolecular compounds, which is mainly used to separate and characterize samples of polymers, proteins, nucleic acids, etc. with different molecular weights. The basic principle is to separate molecules based on their permeation behavior in fillers with specific pore sizes.

　　Gel permeation chromatographThe core principle of the gel filler is to separate molecules with different molecular weights based on their different permeability in the gel filler. The chromatographic column is filled with specific gel materials, usually highly cross-linked polymer particles. These gel particles have specific pore sizes, which can interact with molecular size, resulting in different degrees of molecules entering gel particles according to their size (molecular weight). Smaller molecules can enter the pores of gel particles, while larger molecules cannot, so larger molecules flow faster along the column.

The specific working principle of gel permeation chromatograph is as follows:

1. Sample allocation

At the beginning of the operation, dissolve the sample in an appropriate solvent and inject it into the chromatography column through a syringe. The injected sample will pass through the chromatographic column together with the mobile phase (usually an organic solvent). Under the action of the mobile phase, the sample is carried into the column.

2. Molecular sieve effect

The pores of gel filler have a certain size distribution. Larger molecules flow faster and exit the chromatographic column earlier due to their inability to enter small pores or only entering a small number of pores; Smaller molecules can enter more pores, resulting in slower flow rates and requiring longer time to pass through the chromatographic column.

3. Separation process

In the chromatographic column, the sample is separated by components with different molecular weights. Because smaller molecules can enter more pores, their contact time with gel particles is longer, so their migration speed is slower. Larger molecules cannot enter smaller pores, so they flow faster. Ultimately, molecules are separated within the chromatographic column based on their molecular weight and arrive at the detector at different times.

4. Detection and Data Analysis

UV detectors, refractive index detectors (RI), light scattering detectors (LS), and other detectors are often equipped to monitor and record the composition of samples passing through chromatographic columns. The commonly used detection method is differential refractive index detector, which uses the change in refractive index of the sample solution to monitor different components.

Gel permeation chromatography is an effective tool for molecular weight distribution analysis based on molecular sieve effect. By separating molecules of different molecular weights, the molecular weight and distribution of polymers and other high molecular substances can be accurately characterized. It has a wide range of applications in polymer chemistry, biochemistry, materials science and other fields, especially playing an important role in polymer performance analysis, molecular design, drug research and development.