Gel Permeation Chromatography (GPC) Molecular Weight Testing

Gel permeation chromatography (GPC) is a technique that separates molecules based on their size. Compounds are separated from each other when sample mixtures are passed through a column filled with material of known pore size. This technique is based on the principle of faster decomposition of larger molecules that cannot penetrate the pore size of the packed material (commonly known as the gel).

Essentially, chromatography is a process for separating the components of a mixture. Gel permeation chromatography is often used as a general separation method for semi-volatile compounds. This separation ability is weaker than other types of chromatography. Therefore, gel permeation chromatography is generally used to remove lipids, proteins and natural resins from samples.

Gel permeation chromatography is a very effective method based on differences in molecular mass. Large molecules are extracted and removed from the pores of the gels. This technique can be easily automated.

Gel permeation chromatography has two primary uses:

• Characterizing polymers
• Separating mixtures into separate fractions such as polymer, oligomer, monomer and non-polymer additives

This technique is the only technique available to characterize the molecular weight distribution of polymers. This is a property that all synthetic polymers have.

The main features of gel permeation chromatography can be listed as follows:

• Gel permeation chromatography is a variant of high-performance liquid chromatography (LC).
• Gel permeation chromatography can be performed in a wide variety of solvents, from nonpolar organics to aqueous applications.
• Gel permeation chromatography uses columns filled with very small, round, porous particles to separate molecules contained in the solvent passing through them.
• Gel permeation chromatography separates molecules based on their size, hence also known as size exclusion chromatography.
• The first gel permeation chromatography columns were filled with materials called gels. Therefore, there is gel permeability.
• Gel permeation chromatography is used to determine the molecular weight distributions of polymers.
• The particles in the columns are made of polymers or inorganic materials such as spherical silicas that are cross-linked to make them insoluble.

Molecular weight is a critical property, especially for polymers. Depending on the sample material, molecular weight can be determined by various techniques. The molecular weight and molecular structure of small molecules are determined using mass spectrometry. Using the direct infusion method, samples can be introduced directly into the detector to confirm the molecular weight of a known material or provide structural characterization of an unknown material. The molecular weight information of polymers can be determined using techniques such as viscosity and size exclusion chromatography (gel permeation chromatography). To perform molecular weight determinations of polymers, the solubility of a particular polymer must be understood. In this regard, gel permeation chromatography (GPC) is one of the most widely used methods to determine the molecular weight of polymers. Here, macromolecules are separated based on their molecular size as the sample solution flows through the filled porous gel bed.

Although gel permeation chromatography is a useful and effective tool to evaluate the molecular weight of macromolecular compounds, it is not easy to apply this technique in determining the molecular weight of cationic polymers.

Briefly, size exclusion chromatography, or gel permeation chromatography, is the primary method of determining the molecular weight distribution of a sample. GPC columns are filled with porous beads with a well-defined pore diameter and large pore volume. After injection, small molecules are dragged into the pores, while large molecules are excluded and dragged by the solvent. This separation mechanism results in the removal of analytes from largest to smallest. Precise method development is required to ensure that data are consistent and error-free while minimizing the time spent developing each analysis.

Among the numerous testing, measurement, analysis and evaluation studies provided to businesses by our organization, there are also gel permeation chromatography (GPC) molecular weight testing services.