Methods / SEC

Size-exclusion chromatography

Size exclusion chromatography (SEC) is an analytical technique used to analyze the size distribution of molecules in a sample. SEC separates molecules according to their size in a column filled with fine porous beads.

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Biomass molecular weight distribution

The molar mass distribution of biomass samples soluble in pure water or organic solvents (DMF, DMSO, and THF) is measured with gel permeation chromatography with a refractive index detector (GPC-RID). The system is calibrated with polystyrene and dextran standards. A Pullulan standard is also available upon request. In the case of lignin samples, molar mass distribution is analyzed using size exclusion chromatography (SEC) coupled with a UV detector at 256 nm wavelength. The lignin is dissolved in a suitable solvent before analysis. The SEC system is calibrated with a polystyrene sulfonate standard. A borate buffer is used to set the pH for the eluent.
554 €
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Molecular weight of polymers with GPC/SEC-RI

Gel permeation chromatography (GPC), a.k.a. size exclusion chromatography (SEC), of polymers using a refractive index (RI) detector. This technique will measure the molecular weight distribution of polymer samples in a graphical format, the dispersity, Đ, and determine the molecular weight averages, Mn, Mw, Mz, relative to an existing standard. Please note that the numerical values determined for molecular weight by the RI method are not absolute. GPC/SEC-RI is most commonly used to analyze the graphical distribution or dispersity of a polymer. If you need an absolute determination of your sample's true molecular weight, please see our GPC/SEC-MALS method. Samples must be soluble or capable of being analyzed in solution at room temperature. The type of polymer and the necessary solvent will affect the cost of the measurement. Please contact our experts for a tailored quote.
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Molecular weight of polymers with GPC/SEC-MALS

Gel permeation chromatography (GPC), a.k.a. size exclusion chromatography (SEC), of polymers using a multi-angle light scattering (MALS) detector. This technique will measure the molecular weight distribution of polymer samples in a graphical format, the dispersity, Đ, and determine the actual molecular weight averages, Mn, Mw, Mz. In contrast to other techniques using RI detectors and calibration standards, the MALS method will determine the true molecular weight of the sample. The samples must be soluble or able to be measured from a solution at room temperature. The type of polymer and the necessary solvent will affect the cost of the analysis. Please contact our experts for a quote tailored to your needs.
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Molecular weight of polypropylene with GPC/SEC at high temperatures

Gel permeation chromatography (GPC), a.k.a. size exclusion chromatography (SEC), of polymers using either a refractive index (RI) detector or a multi-angle light scattering (MALS) detector. This product is suitable for polypropylene or polyolefin polymers that are only soluble at high temperatures in 1,2,4-Trichlorobenzene (TCB). This technique will measure the molecular weight distribution of polypropylene (PP) samples in a graphical format, the dispersity, Đ, and determine the molecular weight averages, Mn, Mw, and Mz. Opting for the method with RI detectors will determine the molecular weight relative to a calibration standard. Please note that the numerical values determined for molecular weight by the RI method are not absolute. Opting for the MALS method will determine the true molecular weight of the sample. The choice of detector for the analysis will affect the cost. Please contact our experts for a quote tailored to your needs.
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What is size-exclusion chromatography and how does it work?

Size exclusion chromatography (SEC), also known as gel permeation chromatography (GPC), is an analytical technique that separates molecules based on their size. It is used to analyze the size distribution of the molecules in the sample. With calibration standards, SEC can be used to characterize the molecular weights of unknown molecules. SEC can be used to measure polymers from a few hundred to several million Daltons.

The sample is dissolved in a solvent, and dissolved molecules are separated by their particle size in a column filled with porous beads containing a specific pore size distribution. Since the small molecules diffuse into the pores, the flow of molecules through the column slows down as particle size decreases. Large molecules do not fit in the pores and elute in the void space of the column. Therefore, smaller dissolved molecules flow more slowly through the column than larger molecules, allowing the size distribution to be recorded.

Need an analysis?

Measurlabs offers SEC analyses for the molecular weight distribution analysis of polymers, lignin, and other biomass samples. In addition to conventional SEC/GPC with a refractive index (RI) detector, we also offer SEC-MALS analyses, which yield more meaningful data, especially when analyzing large macromolecules.

Large sample batches and frequent testing can allow for volume discounts - please contact us through the form below to get a tailored quote for your specific need.

Suitable sample matrices

  • Polymers
  • Proteins
  • Macro molecules

Ideal uses of SEC analysis

  • Molecule size distribution characterization
  • Analysis of average molecular weights

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Frequently asked questions

What is SEC commonly used for?

SEC is used to characterize the size distribution of macromolecules.

One common application is the testing of lignin to determine its molecular weight distribution, which varies based on the type of biomass lignin is extracted from.

What are the limitations of SEC?

If the molecules have close molecular weight, it may be difficult to distinguish them leading to uncertainty in the analysis.

What kind of samples can be analyzed with SEC?

Solid macromolecule samples that can be dissolved.

Macromolecule-containing solutions.

What is Measurlabs?

Measurlabs offers a variety of laboratory analyses for product developers and quality managers. We perform some of the analyses in our own lab, but mostly we outsource them to carefully selected partner laboratories. This way we can send each sample to the lab that is best suited for the purpose, and offer high-quality analyses with more than a thousand different methods to our clients.

How does the service work?

When you contact us through our contact form or by email, one of our specialists will take ownership of your case and answer your query. You get an offer with all the necessary details about the analysis, and can send your samples to the indicated address. We will then take care of sending your samples to the correct laboratories and write a clear report on the results for you.

How do I send my samples?

Samples are usually delivered to our laboratory via courier. Contact us for further details before sending samples.