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The preparation of formaldehyde gas mixtures required for metrological assurance of air pollution control is an urgent task. Methods for the preparation of gas mixtures of formaldehyde for metrological purposes are considered. The 2 μmol/mol-level gas mixtures of formaldehyde in nitrogen have been obtained by a dynamic-gravimetric method with the depolymerization of trioxane vapor. The efficiency of the trioxane conversion process was experimentally studied. The sources of uncertainty are analyzed in detail. The reference gas mixtures obtained were used for the formaldehyde mole fraction measurements during the CCQM-K90 key comparison. The relative expanded uncertainty of the measurement U = 3.3% was achieved, confi rmed by the comparison results.

The purpose of this work was to study the contents of calcitonin gene-related peptide (CGRP) and substance P (SP) in the blood plasma of patients with pelvic varicose veins. Thirty women with pelvic varicosities and a reflux blood flow were investigated using duplex ultrasonography. Group 1 included 18 patients with clinical signs of the pelvic congestion syndrome (PCS), including venous pelvic pain (VPP). Group 2 consisted of 12 patients with pelvic varicosities with no clinical signs of PCS. Group 1. The score of VPP intensity ranged from 4 to 8; the mean score being 4.84 0.43. The CGRP level in the studied group ranged from 0.39 to 1.01 ng/mL; the SP level ranged from 0.005 to 1.33 ng/mL. Group 2. The CGRP values were 0.15-0.32 ng/mL, and the SP range was 0.003-0.3 ng/mL. In this group, the levels of the studied peptides were 3-5 times lower than those for the patients with VPP. Group 3. The mean CGRP values were 0.06 0.003 ng/mL, and the mean SP values were 0.03 0.001 ng/mL. These values were considered as the reference parameters; a statistical analysis was performed for them. The correlation analysis revealed a strong relationship between the CGRP and VPP levels (r = 0.82) and a medium correlation between the SP level and pelvic pain in Group 1. The CGRP and SP levels in blood plasma highly correlate with the presence of pelvic venous pain.

New esters of N-benzoyl-3-phenoxyphenylcarboxamide acid and N-benzoyl-N′-4-bromophenyl-3-phenoxybenzamidine were synthesized. Some of the synthesized compounds were shown to inhibit the activity of dipeptidyl peptidase-4 and nonenzymatic glycosylation of proteins and manifested antiplatelet and antioxidant properties. The compounds tested did not display the antagonistic effect toward angiotensin II type 1 receptor, did not influence the activity of glycogen phosphorylase and had very little ability to break cross-links of the glycated proteins. The derivatives with the biological activity of two types were found, which can serve as basic molecules in the search for new drug products.

Main text At the highest metrological level, ammonia gas standards are commonly prepared gravimetrically as Primary Standard Mixtures or using a dynamic standard. This international key comparison addressed the measurement of the amount fraction ammonia in nitrogen, to support calibration and measurement services for mainly environmental applications. The nominal amount fraction was 14 μmol mol-1. The results in this Track C key comparison on the composition of biogas are generally good. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/. 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).

At the highest metrological level, biogas standards are commonly prepared gravimetrically as PSMs (primary standard mixtures). This international key comparison addresses the composition of biogas, to support calibration and measurement services for this renewable energy gas. The mixtures contain nitrogen, carbon dioxide, methane, ethane, propane, hydrogen and oxygen and represent the composition of biogas from landfills. The results in this Track C key comparison on the composition of biogas are generally good. Some of the datasets, especially that of oxygen, showed substantial extra dispersion, that could not be explained by the stated uncertainties. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. 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).

The key comparison CCQM-K137 was aimed at evaluating the level of compatibility of laboratories' preparative capabilities for gravimetric nitrogen monoxide/nitrogen primary reference mixtures at mole fractions of 30 μmol mol-1 and 70 μmol mol-1. The comparison was organised by the BIPM. It consisted in the simultaneous comparison of a suite of 2n primary gas standards, two standards to be prepared by each of the n participating laboratories at the nominal values of 30 μmol mol-1 and 70 μmol mol-1. Two independent analytical methods were used by the BIPM to analyse the amount fraction of nitrogen monoxide (NO) in nitrogen; UV spectrophotometry and chemiluminescence (CLD). The agreement between the results obtained with the two main techniques served to highlight possible issues in the preparation of the standards. During this comparison, standards prepared by two participants appeared to result in a larger bias between the analysers than observed for others. These observations were explained by the analysis of all standards by Fourier Transform Infrared Spectroscopy (FTIR) which identified the presence of a larger amounts of water vapour (H2O), nitrous oxide (N2O) and nitrogen dioxide (NO2) in these standards, which are the three main impurities which can appear in mixtures of NO in nitrogen. The above observations were used to underpin the selection of standards (at each nominal NO mole fraction) which can be considered as a consistent set, allowing the calculation of a calibration line by a Generalised Least-Square regression. Key Comparison Reference Values were then proposed for all participants as predicted values from the calibration lines. Interferences caused in the response of the CLD analyser by impurities (verified by FTIR measurements) led to only the results from the UV analyser being proposed for the KCRV and Degrees of Equivalence calculations. Good agreement was observed between all participants who could prepare their standards with minimum levels of impurities. The key comparison CCQM-K137 is considered to present an analytical challenge at both nominal mole fractions and therefore considered as a Specialised (Track C) comparison in the CCQM nomenclature. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. 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).

Mechanisms of the development of pain in chronic venous diseases (CVD), including pelvic congestion syndrome (PCS), are understudied. The existing hypotheses of the occurrence of venous pelvic pain (VVP) do not allow to answer the question why some patients have no pain syndrome while others have very pronounced pain despite the same morphofunctional changes in the pelvic veins. This review presents current hypotheses of the VPP development, data on some vasoactive neuropeptides (endothelin, calcitonin gene-related peptide, and substance P), their role in the modulation of vascular tone and sensation of pain, possible association between neurogenic inflammation and VPP and provides a rationale for studying the activity of these neurotransmitters in the treatment of PCS and pelvic pain.Механизмы формирования боли при хронических заболеваниях вен, включая синдром тазового венозного полнокровия, до конца не изучены. Имеющиеся гипотезы возникновения венозной тазовой боли не позволяют ответить на вопрос, почему у ряда больных с синдромом тазового венозного полнокровия отсутствует болевой синдром, а у других значительно выражен при одинаковых морфофункциональных изменениях в тазовых венах. В обзоре представлены современные гипотезы формирования венозной тазовой боли, сведения о некоторых вазоактивных нейропептидах (эндотелин, кальцитонин-ген-родственный пептид, субстанция Р), их роли в регуляции сосудистого тонуса и болевых ощущений, возможной связи нейрогенного воспаления и венозной тазовой боли, обосновано потенциальное значение изучения активности указанных нейротрансмиттеров в лечении синдрома тазового венозного полнокровия и тазовой боли.

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 Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. 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).

Interaction of the tetrahedral chalcocyanide cluster anionic complexes of Re, K4[Re4Q4(CN)12] (Q=S, Se, Te), with Ni2+ cationic complexes with polydentate amines, such as ethylenediamine (En), diethylenetriamine (Dien), or triethylenetetraamine (Trien) was used to synthesize six novel complexes: [Ni(NH3)4(En)][{Ni(NH3)(En)2}Re4Te4(CN)12] · 2H2O, [{Ni(En)2}2Re4Se4(CN)12] · 3.5H2O, [Ni(NH3)3(Dien)]2[Re4Se4(CN)12] · 5.5H2O, [{Ni(NH3)2(Dien)}2Re4Te4(CN)12] · 2.5H2O. [Ni(NH3)2(Trien)][{Ni(NH3)(Trien)}Re4Se4(CN)12] · 2.5H2O, [{Ni(Trien)}2Re4S4(CN)12] · 3H2O. The complexes were studied by single-crystal X-ray diffraction analysis.

Three new coordination compounds [{Zn(H2O)2} {Zn(H2O)4} Re4Te4(CN)12] (1), [Zn(en)2(NH3)2][{Zn(en)(NH3)2} Re4Te4(CN)12]·H2O (2), and [{Zn2(dien)3} Re4Te4(CN)12]· ·6H2O (3) (dien is diethylenetriamine) were prepared by reactions of aqueous solutions of the tetrahedral cluster rhenium tellurocyanide complex K4[Re4Te4(CN)12]· 5H2O with zinc dichloride in the presence of ammonia, ethylenediamine, and diethylenetriamine, respectively. Complex 1 has a three-dimensional structure with two types of the Zn atoms; complex 2 is ionic with the polymeric chain anion; complex 3 has a molecular structure. The structures of complexes 1–3 were determined by single-crystal X-ray diffraction analysis.

Reactions of octahedral and tetrahedral chalcocyanide cluster complexes of Re with Cu2+ cations and 1,2S,3S,4-tetraaminobutane (Threo-tab) were used to synthesize and study the structures of the following six novel chiral complexes: [{Cu2(NH3)(Threo-tab)3}Re6S8(CN)6] ⋅ 3H2O (I) (where Threo is 1,2S,3S,4-tetraaminobutane), [{Cu2(NH3)(Threo-tab)3}Re6Se8(CN)6] ⋅ 2H2O (II), [{Cu(Threo-tab)}2Re6Te8(CN)6] ⋅ 13.5H2O (III), [{Cu(Threo-tab)}2Re4Te4(CN)12] ⋅ 6.5H2O (IV), [{Cu2(NH3)(Threo-tab)2}Re4Te4(CN)12] ⋅ 4H2O (V), and [{Cu(NH3)(Threo-tab)}]2[Re4S3.4Te0.6(CN)12] ⋅ 1.25H2O (VI). The structures of complexes I–IV contain extended channels of sufficiently large size capable of including “guest” molecules.

Theoretical concepts of multiple gas extraction are checked experimentally. The possibility is studied of preparing stable gas-vapor mixtures with fixed concentrations of styrene, acrolein, and other volatile organic compounds.

The CCQM-K90 comparison is designed to evaluate the level of comparability of national metrology institutes (NMI) or designated institutes (DI) measurement capabilities for formaldehyde in nitrogen at a nominal mole fraction of 2 μmol mol−1. The comparison was organised by the BIPM using a suite of gas mixtures prepared by a producer of specialty calibration gases. The BIPM assigned the formaldehyde mole fraction in the mixtures by comparison with primary mixtures generated dynamically by permeation coupled with continuous weighing in a magnetic suspension balance. The BIPM developed two dynamic sources of formaldehyde in nitrogen that provide two independent values of the formaldehyde mole fraction: the first one based on diffusion of trioxane followed by thermal conversion to formaldehyde, the second one based on permeation of formaldehyde from paraformaldehyde contained in a permeation tube. Two independent analytical methods, based on cavity ring down spectroscopy (CRDS) and Fourier transform infrared spectroscopy (FTIR) were used for the assignment procedure. Each participating institute was provided with one transfer standard and value assigned the formaldehyde mole fraction in the standard based on its own measurement capabilities. The stability of the formaldehyde mole fraction in transfer standards was deduced from repeated measurements performed at the BIPM before and after measurements performed at participating institutes. In addition, 5 control standards were kept at the BIPM for regular measurements during the course of the comparison. Temporal trends that approximately describe the linear decrease of the amount-of-substance fraction of formaldehyde in nitrogen in the transfer standards over time were estimated by two different mathematical treatments, the outcomes of which were proposed to participants. The two treatments also differed in the way measurement uncertainties arising from measurements performed at the BIPM were propagated to the uncertainty of the trend parameters, as well as how the dispersion of the dates when measurements were made by the participants was taken into account. Upon decision of the participants, the Key Comparison Reference Values were assigned by the BIPM using the largest uncertainty for measurements performed at the BIPM, linear regression without weight to calculate the trend parameters, and not taking into account the dispersion of dates for measurements made by the participant. Each transfer standard was assigned its own reference value and associated expanded uncertainty. An expression for the degree of equivalence between each participating institute and the KCRV was calculated from the comparison results and measurement uncertainties submitted by participating laboratories. Results of the alternative mathematical treatment are presented in annex of this report. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. 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).

This article presents the report on the COOMET key comparison COOMET.QM-K111, which is linking to the appropriate CCQM comparison—CCQM-K111 'Propane in nitrogen 1000 μmol/mol'. CCQM-K111 was carried out in 2014–2016 and it was one of a series of key comparisons in the gas analysis area assessing core competences. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. 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).

Carbon monoxide (CO) is reported to mainly be emitted from industries, transportation, and burnings for various usages. Its atmospheric lifetime varies from weeks to months, depending on the mixing ratio of the highly reactive hydroxyl radical. Even though the ambient level of CO varies as a function of regional sources, the mixing ratio ranges from 30 nmol/mol to 300 nmol/mol at the marine boundary layers and from 100 nmol/mol to more than 500 nmol/mol in urban areas(1). In order to study temporal trends and regional variations of the level of CO, the National Oceanic & Atmospheric Administration/Earth System Research Laboratory-Global Monitoring Division (NOAA/ESRL-GMD(2)) has played a key role as the designated Central Calibration Laboratory (CCL) within the frame of the World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) program. NOAA/ESRL-GMD provides natural air standards, analyzed for CO, to WMO GAW participants. Since the structure of WMO traceability chain appears hierarchical and explicit all over the world, WMO intends to improve the CO measurement compatibility to up to 2 ppb (in case of extensive compatibility goal: 5 ppb, GAW report No. 213(3)) in order to ensure compatibility through the GAW network. Nevertheless, accurate measurement of CO at an ambient level has proven to be difficult due to the lack of stability in cylinders. For these reasons, it is necessary that measured results are compared among the values assigned by various NMIs. This key comparison was initially proposed to be aimed at a CO/N2 standard in the 2010 CCQM meeting by KRISS. With participation of FMI, NOAA, and Empa, a modified scheme of CO/air standards was developed for the purpose of atmospheric observations and co-operative support to WMO/GAW activities. Therefore, the purpose of the comparison is to support the measurement capability of CO at an ambient level of 350 nmol/mol. Further, this key comparison is expected to contribute to the establishment of traceability to a single scale of CO between NMIs by means of harmonizing the results from different national standards. The Empa result lies in a different report. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. 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).

This article presents the report on the COOMET supplementary comparison "Atmospheric air pollutants: CO in Nitrogen, 5 μmol/mol". Carbon monoxide (CO) is present in atmosphere due to different natural and anthropogenic sources. CO is a toxic gas and in concentrations higher than (3-5) μmol/mol it is hazardous to human health. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. 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).

This key comparison aims to assess the core capabilities of the participants in gas analysis. Such competences include, among others, the capabilities to prepare primary standard gas Mixtures (PSMs), perform the necessary purity analysis on the materials used in the gas mixture preparation, the verification of the composition of newly prepared PSMs against existing ones, and the capability of calibrating the composition of a gas mixture. According to the Strategy for Key Comparisons of the Gas Analysis Working Group, this key comparison is classified as a track A key comparison, which means that the results of this key comparison can be used to underpin calibration and measurement capabilities using the flexible scheme, and for propane under the default scheme. The artefacts were binary mixtures of propane in nitrogen at a nominal amount-of-substance fraction level of 1000 μmol/mol. The values and uncertainties from the gravimetric gas mixture preparation were used as key comparison reference values (KCRVs). Each transfer standard had its own KCRV. The results are generally good. All results but one are within ± 0.2 % of the KCRV. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. 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).

Dimethyl sulfide (DMS) is an important compound in monitoring climate change and is monitored by the World Meteorological Organization Global Atmospheric Watch Volatile Organic Compounds (WMO-GAW VOC) program at several monitoring sites. It is essential that measurement results are accurate and consistent among the assigned values for primary gas mixtures to meet the WMO requirement. The purpose of this comparison is to compare the measurement capability of DMS at approximately 10 μ­mol/mol and expectation to contribute the establishment of traceability to single measurement scale for DMS between NMIs. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. 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).

COOMET.QM-S3 is a supplementary comparison of primary standard gas mixtures—'Carbon monoxide in Nitrogen (3 μmol/mol)'. This is a bilateral comparison between VNIIM and INMETRO and it was conducted in 2013. Carbon monoxide is a toxic gas and in concentrations higher than 3–5 μmol/mol it is hazardous to human health. Therefore, it is important for NMIs to have the capability of an accurate carbon monoxide measurements. This comparison has shown that primary standard gas mixtures of carbon monoxide in nitrogen on the level of 3 μmol/mol, prepared in VNIIM and Inmetro, do not agree—the pair-wise degree of equivalence D (0.77%) is higher than the appropriate expanded uncertainty U(D) (0.29%). Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. 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).

The relevance of the COOMET.QM-K93 comparison is founded on paying particular attention to reliability of measurements which are performed during the medical examination of drivers of vehicles in order to assess the degree of alcoholic intoxication. Standard gas mixtures of ethanol in nitrogen in cylinders under pressure play a key role in providing metrological assurance of breath-alcohol analyzers. Participating laboratories: VNIIM and Ukrmetrteststandart. This comparison was carried out in 2014-2015. This supplementary comparison supports CMC claims for: ethanol in the range 50–500 μmol/mol in a matrix of either nitrogen or synthetic air. Results: The results are consistent with the reference values. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. 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).

Sulfur dioxide is one of the main contaminants present in the atmosphere due to burning of coal, oil and natural gas, smelting of base metals and production of sulfuric acid. Sulfur dioxide has been the subject of three previous CCQM key comparisons: CCQM-K1.d in 1997, CCQM-K26.b in 2005 and CCQM-K76 in 2010. VNIIM proposed a new COOMET project (No 484/RU/09) in this field, which was registered in the KCDB as key comparison COOMET.QM-K76. It was found that all results were consistent with the reference (gravimetric) values, with observed differences not exceeding ?0.60% and not exceeding either the appropriate assigned expanded uncertainties. VNIIM is the linking laboratory to CCQM-K76. SMU has improved the results obtained in CCQM-K76. The mixtures prepared for this exercise were found to be stable during about one year within the uncertainty of the measurements. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. 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).

Nitrogen monoxide is one of the main contaminants present in the atmospheric air due to emissions of vehicles and power stations. Taking into account the positive experience of VNIIM in the pilot study CCQM-P73 (Nitrogen monoxide gas standards, 30 ?mol/mol to 70 ?mol/mol), a COOMET project (No 483/RU/09) on the subject was decided and registered in the KCDB as supplementary comparison COOMET.QM-S1. This involved six National Metrology Institutes, aiming to consolidate or support their Calibration and Measurement Capabilities in this field. It was found that most of the results were consistent with the reference (gravimetric) values, with observed differences not exceeding ?1.3% and not exceeding either the appropriate assigned expanded uncertainties. There was, however, one exception: the INMETRO difference from the reference value is slightly higher than the expended uncertainty. The mixtures prepared for this exercise were found to be stable during about one year within the uncertainty of the measurements. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by COOMET, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

The aim of this comparison is to evaluate the gravimetry and purity verification of gas mixtures prepared by introducing a liquid into a gas cylinder. This type of preparation is well known from, e.g., ethanol in nitrogen/air (CCQM-K4), and n-hexane in synthetic natural gas (CCQM-K16). The choice for n-hexane in methane is based on the relevance of natural gas primary standard mixtures and higher hydrocarbons in synthetic natural gas (for, e.g., dew point calibrations). Furthermore, n-hexane is relatively straightforward to analyse using a GC/FID (gas chromatograph equipped with a flame ionisation detector) with good repeatability. Eight laboratories participated. After the data evaluation, the result of one laboratory was eliminated to arrive at a consistent subset. The quality of the fitted line was not overly good, leading to small discrepancies in the degrees-of-equivalence calculated for three other laboratories. Only four laboratories are consistent with the KCRV. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

The key comparison CCQM-K65 was intended to compare the capabilities for the preparation and value assignment of gas standards for methyl and ethyl mercaptans in methane, maintained at the participating national metrological institutes: VNIIM (Russia), KRISS (Korea), VSL (Netherlands) and NPL (United Kingdom). The range of the nominal amount of substance fractions of the comparison gas mixtures was 20 µmol/mol to 30 µmol/mol, which is close to regulatory level (in several countries including Russia) for mercaptans in odorated natural gas. This comparison was proposed at the 12th GAWG meeting in October 2004 and was conducted in 2008. Conclusions are as follows: The results of all laboratories are consistent with the reference values. The observed differences between the reference and reported values are within ±0.9% for methyl mercaptan and ±0.75% for ethyl mercaptan relative to the gravimetric values, and do not exceed the appropriate assigned expanded uncertainties. The prepared mixtures were found to be stable during about a year within the uncertainty of the measurements. The gravimetric values were successfully validated with a dynamic method. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

The first key comparison on carbon dioxide in nitrogen dates from 1993–1994 (CCQM-K1.b). Since then, numerous national metrology institutes (NMIs) have been setting up facilities for gas analysis, and have developed claims for their Calibration and Measurement Capabilities (CMCs) for these type mixtures. In the April 2005 meeting of the CCQM Gas Analysis Working Group, a policy was proposed to repeat key comparisons for stable mixtures every 10 years. Consequently in 2007 the key comparison CCQM-K52 'Carbon dioxide in synthetic air' was carried out. This comparison is consistent with the proposed policy and enables NMIs that could not participate in the previous comparison to take part. This report describes the results of a key comparison for carbon dioxide in synthetic air. The amount-of-substance fraction level of carbon dioxide chosen for this key comparison (360 µmol/mol) represents the ambient level of this component in air. In total 18 NMIs and one WMO laboratory participated in the comparison. The agreement of the results in this key comparison is very good. With a few exceptions, the results agree within 0.3% (or better) with the key comparison reference value. Most of the participants that did not participate in CCQM-K1.b do very well. In some cases, the uncertainties claimed are quite large in comparison with the NMIs for which this comparison is a true 'repeat', but the observed differences with the KCRV usually reflect that these claims are realistic. All participants in CCQM-K1.b that participated in this key comparison show improved results. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

At the highest metrological level, natural gas standards are commonly prepared gravimetrically as PSMs (primary standard mixtures). This international key comparison is a repeat of CCQM-K1e-g. The mixtures concerned contain nitrogen, carbon dioxide and the alkanes up to butane. The only difference with CCQM-K1e-g is the addition of iso-butane to the list. The results usually agree within 1% (or better) with the key comparison reference value. For ethane, nitrogen and carbon dioxide, the agreement is within 0.5% (or better), and for methane within 0.1% (or better) of the KCRV. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

1. Characterisation of the thermal stability of cellulose acetate merely from the yellowing intensity does not reflect the changes in the degree of polymerisation during heat treatment. Therefore, we cannot always assess the destructive processes occurring in the specimen from the degree of yellowing of cellulose acetate. 2. It is desirable to monitor production batches of cellulose acetate [3] not only from the change in colour during heat treatment, but also from the resistance to destruction, characterised by the viscosity.