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International comparison CCQM-K10.2018: BTEX in nitrogen at 5 nmol mol−1



Christina Cecelski, George C. Rhoderick, Antonio Possolo, Jennifer Carney, Miroslav Vokoun, Jitka Privoznikova, Sangil Lee, Ji Hwan Kang, Yong Doo Kim, Dal Ho Kim, Tatiana Mace, Christophe Sutour, Celine Pascale, Napo Ntsasa, James Tshilongo, Mudalo Jozela, Nompumelelo Leshabane, Goitsemang Lekoto, David Worton, Paul Brewer, Fred Farrow-Dunn, Sergi Moreno, Klaus Wirtz, Volker Stummer, L.A. Konopelko, A.V. Kolobova, Y.A. Kustikov, A.Y. Klimov, O.V. Efremova, Janneke van Wijk, Adriaan van der Veen


The CCQM-K10.2018 comparison aimed to evaluate the capabilities of national metrology institutes (NMIs) to prepare and/or value assign primary reference mixtures containing benzene, toluene, ethylbenzene, p-xylene, m-xylene and o-xylene (subsequently referred to as BTEX) in nitrogen. This key comparison was separated into two parallel studies. The first study, deemed the "gravimetric study", evaluated the level of compatibility of BTEX standards provided by NMIs. Seven participating laboratories each submitted one standard at nominal 5 nmol mol-1 BTEX in nitrogen. Comparison measurements were performed by the National Institute of Standards and Technology (NIST) from July to October 2018. The second study, deemed the "comparative study", compared the capabilities of NMIs to measure the amount fractions of BTEX in a mixture provided by NIST. NIST prepared one standard at nominal 5 nmol mol-1 BTEX in nitrogen, which was measured consecutively by three participating laboratories. The participants' measurements took place from August 2018 to March 2019. The comparison protocol adopted for CCQM-K10.2018 was more challenging than for the original comparison, CCQM-K10 in 2001, and the results provide an extended evaluation of the level of compatibility of BTEX in nitrogen standards.


BTEX, gas mixture, CCQM, key comparison


Cecelski, C. , Rhoderick, G. , Possolo, A. , Carney, J. , Vokoun, M. , Privoznikova, J. , Lee, S. , Kang, J. , Kim, Y. , Kim, D. , Mace, T. , Sutour, C. , Pascale, C. , Ntsasa, N. , Tshilongo, J. , Jozela, M. , Leshabane, N. , Lekoto, G. , Worton, D. , Brewer, P. , Farrow-Dunn, F. , Moreno, S. , Wirtz, K. , Stummer, V. , Konopelko, L. , Kolobova, A. , Kustikov, Y. , Klimov, A. , Efremova, O. , van Wijk, J. and van der Veen, A. (2022), International comparison CCQM-K10.2018: BTEX in nitrogen at 5 nmol mol−1, Metrologia, [online],, (Accessed May 19, 2024)


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Created February 18, 2022, Updated November 29, 2022