International comparison CCQM-K51: Carbon monoxide (CO) in nitrogen (5 µmol mol−1)

The first key comparison on carbon monoxide (CO) in nitrogen dates back to 1992 (CCQM-K1a). It was one of the first types of gas mixtures that were used in an international key comparison. 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 mixtures. Furthermore, in the April 2005 meeting of the CCQM (Consultative Committee for Amount of Substance) Gas Analysis Working Group, a policy was proposed to repeat key comparisons for stable mixtures every 10 years. This comparison was performed in line with the policy proposal and provided an opportunity for NMIs that could not participate in the previous comparison. NMISA from South Africa acted as the pilot laboratory. Of the 25 participating laboratories, 19 (76%) showed satisfactory degrees of equivalence to the gravimetric reference value. The results show that the CO concentration is not influenced by the measurement method used, and from this it may be concluded that the pure CO, used to prepare the gas mixtures, was not 13C-isotope depleted. This was confirmed by the isotope ratio analysis carried out by KRISS on a 1% mixture of CO in nitrogen, obtained from the NMISA. There is no indication of positive or negative bias in the gravimetric reference value, as the results from the different laboratories are evenly distributed on both sides of the key comparison reference value

Development of benzene, toluene, ethyl benzene, m-xylene, p-xylene and o-xylene (BTEX) gas reference standards for air pollution monitoring in South Africa

Direct monitoring of volatile organic compounds emitted from industrial sources as well as the monitoring of ambient levels thereof in the atmosphere play an important role in providing data for various legislative requirements. There are many volatile organic compounds emitted to the atmosphere, from biomass burning, power stations, and many other sources. Primary reference gas mixtures of volatile organic compounds containing six components, namely benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene (BTEX) were prepared by gravimetric methods at nominal amount of substance fractions of 10 µmol/mol. The preparation was performed using the stainless steel (loop) method and direct liquid injection method using gas tight syringe connected to a dedicated syringe heater for comparison purposes. The results of the gravimetric values for both methods were within 1 % of the nominal amount of substance fraction. After the preparation, comparison was achieved by analysis of the BTEX gas mixtures using gas chromatography with flame ionisation detection (GC-FID) and showed comparability to within 2 % of the gravimetric values. The contributions to the uncertainty of measurement were from weighing stainless steel tubes, syringes, and gas cylinders, as well as purity data. The contribution to the uncertainty of measurement from the analysis by GC-FID were repeatability and reproducibility. The combined expanded uncertainty of measurement was between 1.09 % and 3.51 %. The larger deviation from the gravimetric values and associated uncertainty was observed for benzene due to its higher volatility compared to the other components. The BTEX reference gas mixtures prepared in this study are currently being used as a source of traceability in South Africa for air pollution monitoring purposes.Open access funding provided by Mintek.http://link.springer.com/journal/769Chemistr

Removal of Nickel from Nickel Sulfite-Fire Assay Dissolution Filtrate Through Precipitation

This study responds to stringent environmental regulations and increasing focus on resource conservation by exploring economically viable refining technologies through recycling. With the rising costs of filtrate disposal, there is a significant emphasis on removing and recycling valuable constituents, particularly nickel and copper (Ni and Cu). Herein, we employ analytical techniques with the aim of investigating an alternative method for recovering Ni and other valuable metals from a nickel sulfide-fire assay filtrate using S-curve precipitation under optimal conditions. The waste from the fire assay procedure contains substantial amounts of Ni and other critical metals, with concentrations of 62.7 g/L of Ni and 3.87 g/L of Cu. Prior to precipitation, traditional solvent extraction was used for Cu extraction, selectively removed before separating primary impurities such as iron (Fe). A pivotal aspect of this research involves applying S-curve precipitation with precise parameters at different pH levels. Analytical techniques reveal a minor depletion occurs as Ni is separated from Fe at a pH of 2.5, resulting in the formation of a refined Ni stream that is then refined into a mixed hydroxide Ni(OH)2 product. The efficiency of 5,8-diethyl-7-hydroxydodecan-6-oxime (LIX 63–70) in extracting value-added metals from fire assay waste is exceptionally high, integrating recycling and repurposing of value-added base metals to promote a circular economy

CCQM-K120 (Carbon dioxide at background and urban level)

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

International Comparison CCQM-K51 - Carbon Monoxide (CO) in Nitrogen (5 µmol mol-1)

The first key comparison on carbon monoxide (CO) in nitrogen dates back to 1992 (CCQM-K1a). It was one of the first types of gas mixtures that were used in an international key comparison. 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 mixtures. Furthermore, in the April 2005 meeting of the CCQM (Consultative Committee for Amount of Substance) Gas Analysis Working Group, a policy was proposed to repeat key comparisons for stable mixtures every 10 years. This comparison was performed in line with the policy proposal and provided an opportunity for NMIs that could not participate in the previous comparison. NMISA from South Africa acted as the pilot laboratory. Of the 25 participating laboratories, 19 (76%) showed satisfactory degrees of equivalence to the gravimetric reference value. The results show that the CO concentration is not influenced by the measurement method used, and from this it may be concluded that the pure CO, used to prepare the gas mixtures, was not 13C-isotope depleted. This was confirmed by the isotope ratio analysis carried out by KRISS on a 1% mixture of CO in nitrogen, obtained from the NMISA. There is no indication of positive or negative bias in the gravimetric reference value, as the results from the different laboratories are evenly distributed on both sides of the key comparison reference value.JRC.H.2-Air and Climat

International comparison CCQM-K76 : sulfur dioxide in nitrogen

85 p. : il.This Key Comparison is designed to test the capabilities of the participants to measure and certify sulfur dioxide in nitrogen, and will provide supporting evidence for the CMCs of institutes for sulfur dioxide. Also, as sulfur dioxide is designated a core compound, and the 100 μmol/mol concentration is within the designated core compound concentration range, this comparison is also designed to demonstrate core capabilities of institutes which qualify under the rules of the Gas Analysis Working Group

International comparison CCQM K52: carbon dioxide in synthetic air

61 p. : il.The first key comparison on carbon dioxide in nitrogen dates from 1993-1994 (CCQM-K1b) [1]. It is in fact one of the first types of gas mixtures that was used in an international (key) comparison. 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 mixtures. Also, in 2003 a comparison (CCQM-P41 [2, 3]) was carried out between NMIs and WMO laboratories for the determination of greenhouse gases showing a good overall agreement between the participants. 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, 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 (oxygen + nitrogen). 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. This key comparison aims to support CMC-claims for carbon dioxide in both nitrogen or air (synthetic and purified) from 100 μmol/mol to 20 cmol/mol