Gel Permeation Chromatography - Multi-Angle Static Light Scattering (GPC-MALS)

GPC (gel permeation chromatography) technique is widely used to separate macromolecules of different sizes based on the partially exclusion of these molecules from the pores of stationary phases. However, conventional GPC using a single concentration-sensitive detector may suffer from limitations and drawbacks that lead to incorrect or even cryptic information about the polymer samples. In addition, GPC relies on calibration of standard polymers of known molecular weight to determine the molecular weight of an unknown sample. However, for branched polymers or structurally complex polymers, this method can produce inaccurate results due to differences in hydrodynamic volume compared to linear polymers of the same nominal molecular weight. By introducing multi-angle light scattering (MALS) into GPC, these limitations can be overcome, resulting in improved molecular weight determination, enhanced structural characterization, and expanded analytical capabilities for polymer analysis.

Principle of GPC-MALS

• In GPC, samples are separated according to the fluid volume of different molecules. Specifically, the column is filled with packing particles with many small holes on the surface. When the samples flow through the packing with the mobile phase, the smaller molecules can enter the packing particles through the holes on the surface. The larger particles can only pass through the gap between the packing particles. Over time, molecules of different sizes contained in the sample become separated due to the length of the path they take. By adjusting the pore size of the surface of the packing particle, the sample of a certain molecular size range can be separated.
• As the components leave the column, they are exposed to the laser. As the laser passes through the sample, the light is scattered and picked up by the detector. The intensity of scattered light at each angle is directly proportional to the molar mass and concentration of the molecule being studied. With further calculations, these data can also provide information on the level of branching, conformation, and conjugation in the molecule.

Applications of GPC-MALS

GPC-MALS is often used to help determine molecule sizes, shapes, and conformations of large macromolecules, such as biotherapeutics, proteins, polymers and more in the fields of biological and materials science.

• Research and structural characterization of biological macromolecules, such as proteins, peptides, polysaccharides (starch, polyacrylamide, melon gum, etc.) and various artificial biological materials (e.g. polylactic acid);
• Research and structural characterization of polymers, such as PS, PMMA, PAM and other polymers;
• Precise characterization of low molecular weight polymers (<10,000D);
• Precise determination of ultra-large molecular weight polymers (such as modified starch);
• Hyperbranched polymers and complex morphology;
• Accurate determination of aggregates with very low content, such as natural polymers in research fields like biology, food science and agronomy (with low content and complex components), with detection sensitivity as low as 10 ng.

Sample Requirements

As GPC-MALS is performed in solution, any solid sample material needs to be dissolved in a suitable solvent for the column. Some samples, especially biomolecules, may require additional buffer solutions that must be matched to the column. Large particles can block the column, so the solution may need to be filtered to ensure it is free of solid debris before analysis.

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