Brunauer-Emmett-Teller (BET) analysis

Brunauer-Emmett-Teller (BET) theory can be used to determine the specific surface area of solid materials based on gas adsorption measurements. Gas adsorption is a powerful technique for determining critical information about the structure of solid materials. The method is suitable for analyzing a wide range of solid matrices from catalyst powders to monolithic materials.

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What is BET analysis?

While BET technically refers to the theory used in the determination of specific surface area, the term is often extended to refer to surface area and pore size measurement by gas adsorption more broadly. The analysis is based on the physical adsorption of inert gas, such as nitrogen and krypton, on the solid surface of the sample. The measured specific surface area is given in m2/g.

What is BET analysis used for?

BET specific surface area is an important parameter used for the characterization of a wide range of solids. For example, it is used for analyzing the fineness of cement and concrete and the adsorption capability of activated carbon, for the characterization of drug delivery systems of pharmaceuticals and the adsorption performance of gas purifiers, for catalyst characterization, and for studying nanomaterials. Nanomaterial identification can be based on measuring the volume-specific surface area (VSSA), which can be determined using BET analysis and He pycnometry.

How is surface area determined by gas adsorption?

The BET specific surface area of a sample is determined by the adsorption of an inert gas on the sample surface. The properties of the sample define the suitable inert gas for the analysis. Usually, nitrogen is suitable for materials with a specific surface area greater than 1 m2/g, while krypton is used for materials with smaller specific surface areas.

Sample preconditioning is an essential step before starting the gas adsorption measurement. All possible physically bonded surface impurities including moisture must be removed via a degassing step. The degassing step is performed under vacuum conditions and at high temperatures, usually with the same gas adsorption instrument. 

After degassing the sample at appropriate conditions, the sample is exposed to cryogenic temperatures (usually liquid nitrogen at 77K) and an adsorbate gas with controlled pressure. Adsorption occurs as the gas molecules are attracted to the surface of the solid sample, creating physical bonds with the surface.  The amount of gas adsorbed is monitored at each pressure point, which is used to create the adsorption isotherm. BET analysis is done at the initial point(s) of the isotherm, which represents the monolayer adsorption of gas molecules on the sample surface.

How many points on the isotherm should be used for the calculation depends on the sample and the objective of the analysis. Single point measurement is usually offered for established materials with known specific surface area, mostly used for quality checks as a quick and easy approach. For unknown materials, multi-point analysis is recommended. 

Sample requirements and preparation

BET analysis is suitable for the characterization of powders and monolithic solids. Usually, around 500 mg to 1 g of sample material is needed to obtain reliable results, but sometimes smaller or greater sample amounts might be needed, depending on the density of the sample.

Need a BET analysis?

Measurlabs offers BET analysis services of high quality with fast results and affordable prices. If you have any questions about your sample or its suitability for the method, our experts are always happy to help. You can contact us through the form below or by emailing us at

Suitable sample matrices

  • Cement
  • Concrete
  • Pharmaceutical ingredients
  • Minerals
  • Activated carbon
  • Carbon nanotubes
  • Zeolits
  • Other powders and porous materials

Ideal uses of BET analysis

  • Assessing the adsorption capability of materials
  • Quality control in metallurgy, pharmaceuticals, cement, and concrete industries
  • Characterization of catalysts
  • Research on powder metallurgy and nanomaterials
  • Porous molecular sieve development
  • Gas filtration development

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Frequently asked questions

What is BET analysis commonly used for?

BET analysis is mainly used for analyzing the fineness of cement and concrete, the adsorption capability of activated carbon, catalyst characterization, the adsorption performance of gas purifiers, and for studying nanomaterials.

What kinds of samples are suitable for BET analysis?

Powders and monolithic solids like cement, concrete, minerals, zeolites, carbon, and pharmaceutical ingredients can be analyzed with BET.

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.