3P Instruments specifies standard materials according to ISO 9277:2010 and IUPAC recommendation of 2015 also for Argon 87 K measurements
A considerable number of users of gas sorption devices are now changing their standard adsorptive for scientific surface and pore analysis to argon at a measuring temperature of 87 K. This is due to the problems of nitrogen sorption at 77 K, which are described in the BET standard ISO 9277 /1/ and also in the IUPAC recommendation for the analysis of specific surfaces and micropores of 2015. As a certified company, 3P Instruments takes this development into account and has now added results of standard-compliant argon sorption measurements to the specification of two standard materials:
- BET-Standard 3P-SRF-586
The granulated alumina BET standard 3P-SRF-586 is used to check the BET analyzers serviced by 3P and is a basis for our equipment maintenance and service repairs. It was previously specified only for traditional N2 77 K measurements. However, since the nitrogen molecule has the known problems for the scientific determination of specific surfaces /1 – 3/, instrument manufacturers should also offer instrument testing with the recommended argon adsorptive.
The data sheet for the standard 3P-SRF-586 illustrates the differences: At 5.86 m2/g, the BET surface from N2 77 K measurements is more than 20 % overestimated compared to the BET surface determined with the noble gas argon. With the BET Standard 3P-SRF-586, it is now possible to ensure that your measuring instruments from different manufacturers operate correctly in accordance with the standard recommendations of ISO and IUPAC. For scientific work, but also in the context of upcoming laboratory accreditations and certifications, the device verification under standard conditions can be a reproducible basis for proper analytical results. The article number of this universal BET-Ar 87 K standard is 96397.
- Micropore standard 3P-AC-reference
For this spherical activated carbon, the BET surface area as well as total and micropore volumes from isotherms of N2 77 K, Ar 87 K and CO2 273 K were specified. Furthermore, the data sheet contains typical example isotherms for this microporous standard for all three adsorptives. A general discussion of the problem of different results of different adsorptives can be found in /3/, and and can also be requested here. For the evaluation of the sorption isotherm, the BET method in the relative pressure range adapted for micropores, the Gurvich rule for the total pore volume and the Dubinin-Radushkevich (DR) evaluation for the micropore volume are used for the micropore standard. The article number of this universal micropore Ar 87 K standard is 170183.
If you would like to discuss possible evaluation models, measurement routines as well as tips & tricks for your special measurement tasks with us: our training seminar will take place in Leipzig in November 2020. We are looking forward to meeting you (of course with due consideration of contact precautions). Our Laboratory for Scientific Particle Analysis (LabSPA) operates BET instruments from three instrument manufacturers and can certainly provide you with recommendations and experience for (almost) any task.
/1/ ISO 9277:2010: Determination of the specific surface area of solids by gas adsorption – BET method
/2/ IUPAC recommendation, Pure Appl. Chem. 87 (9-10), 1051-1069 (2015); pdf-Download
/3/ 3P Yellow paper 2 – 1, Adsorption studies of porous and nonporous materials with various adsorptives in the entire temperature range from 77 K up to 323 K