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Mass fraction assignment of folic acid in a high purity material

Westwood, Steven,Josephs, Ralf,Choteau, Tiphaine,Daireaux, Adeline,Stoppacher, Norbert,Wielgosz, Robert,Davies, Stephen,Rego, Eliane de,Wollinger, Wagner,Garrido, Bruno,Fernandes, Jane,Lima, Jonathan BUREAU INTERNATIONAL DES POIDS ET MESURES 2018 METROLOGIA -BERLIN- Vol.55 No.1
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International comparison CCQM-K82: methane in air at ambient level (1800 to 2200) nmol/mol

Flores, Edgar,Viallon, Joë,le,Choteau, Tiphaine,Moussay, Philippe,I Wielgosz, Robert,Kang, Namgoo,Moon Kim, Byung,Zalewska, Ewelina,(A M H) van der Veen, Adriaan,Konopelko, Leonid,Wu, Hai,Han, Qia IOP 2015 Metrologia Vol.52 No.-
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The CCQM-K82 comparison was designed to evaluate the degrees of equivalence of NMI capabilities for methane in air primary reference mixtures in the range (1800 to 2200) nmol/mol. The balance gas for the standards was either scrubbed dry real air or synthetic air. CH4 in air standards have been produced by a number of laboratories for many years, with more recent developments focused on standards at atmospheric measurement concentrations and aimed at obtaining agreement between independently produced standards. A comparison of the differences in primary gas standards for methane in air was previously performed in 2003 (CCQM-P41 Greenhouse gases. 1 and 2) with a standard deviation of results around the reference value of 30 nmol/mol and 10 nmol/mol for a more limited set of standards. This can be contrasted with the level of agreement required from field laboratories routinely measuring atmospheric methane levels, set by Data Quality Objectives (DQO) established by the World Meteorological Organization (WMO) to reflect the scientifically desirable level of compatibility for CH4 measurements at the global scale, currently set at 2 nmol/mol (1 sigma). The measurements of this key comparison took place from May 2012 to June 2012. Eight laboratories took part in this comparison coordinated by the BIPM and NIST. Key comparison reference values were calculated based on Cavity Ring Down Spectroscopy Measurements performed at the BIPM, combined with participant's gravimetric values to identify a consistent set of standards. Regression analysis allowed predicted values for each standard to be calculated which acted as the KCRVs. In this comparison reported standard uncertainties by participants ranged from 0.50 nmol/mol to 2.4 nmol/mol and the uncertainties of individual KCRVs ranged from 0.68 nmol/mol to 0.71 nmol/mol. The standard deviation of the ensemble of standards about the KCRV value was 1.70 nmol/mol. This represents a greater than tenfold improvement in the level of compatibility of methane in air standards compared to that demonstrated in 2003. Further improvements in the compatibility of standards will require improved methods and uncertainties for the measurement of trace level methane in balance gases. Main text. To reach the main text of this paper, click on <A HREF='http://www.bipm.org/utils/common/pdf/final_reports/QM/K82/CCQM-K82.pdf'>Final Report</A>. Note that this text is that which appears in Appendix B of the BIPM key comparison database <A HREF='http://kcdb.bipm.org/'>kcdb.bipm.org/</A>. The final report has been peer-reviewed and approved for publication by CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
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CCQM-K120 (Carbon dioxide at background and urban level)

Flores, Edgar,Viallon, Joë,le,Choteau, Tiphaine,Moussay, Philippe,Idrees, Faraz,Wielgosz, Robert I,Lee, Jeongsoon,Zalewska, Ewelina,Nieuwenkamp, Gerard,Veen, Adriaan van der,Konopelko, L A,Kustiko BUREAU INTERNATIONAL DES POIDS ET MESURES 2019 METROLOGIA -BERLIN- Vol.56 No.-
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 CCQM-K120.a comparison involves preparing standards of carbon dioxide in air which are fit for purpose for the atmospheric monitoring community, with stringent requirements on matrix composition and measurement uncertainty of the CO2 mole fraction. This represents an analytical challenge and is therefore considered as a Track C comparison. The comparison will underpin CMC claims for CO2 in air for standards and calibrations services for the atmospheric monitoring community, matrix matched to real air, over the mole fraction range of 250 μmol/mol to 520 μmol/mol. CCQM-K120.b comparison tests core skills and competencies required in gravimetric preparation, analytical certification and purity analysis. It is considered as a Track A comparison. It will underpin CO2 in air and nitrogen claims in a mole fraction range starting at the smallest participant's reported expanded uncertainty and ending at 500 mmol/mol. Participants successful in this comparison may use their result in the flexible scheme and underpin claims for all core mixtures This study has involved a comparison at the BIPM of a suite of 44 gas standards prepared by each of the participating laboratories. Fourteen laboratories took part in both comparisons (CCQM-K120.a, CCQM-K120.b) and just one solely in the CCQM-K120.b comparison. The standards were sent to the BIPM where the comparison measurements were performed. Two measurement methods were used to compare the standards, to ensure no measurement method dependant bias: GC-FID and FTIR spectroscopic analysis corrected for isotopic variation in the CO2 gases, measured at the BIPM using absorption laser spectroscopy. Following the advice of the CCQM Gas Analysis Working Group, results from the FTIR method were used to calculate the key comparison reference values. KEY WORDS FOR SEARCH FTIR, CO2, GC-FID, Carbon dioxide at background level, Carbon dioxide at urban level, Delta Ray, CO2 gas standards <H2>Main text</H2> To reach the main text of this paper, click on <A HREF='https://www.bipm.org/utils/common/pdf/final_reports/QM/K120/CCQM-K120.pdf'>Final Report</A>. Note that this text is that which appears in Appendix B of the BIPM key comparison database <A HREF='http://kcdb.bipm.org/'>kcdb.bipm.org/</A>. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

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