Features and problems of metrological traceability of gas mixtures using UV absorption, FTIR, and CRD spectroscopy

Metrological traceability is usually realized by comparing the high precision gas mixtures (reference standards (RS)) and working standards used for calibration of gas analyzers. The procedures with the use of UV absorption, FTIR, and CRD spectroscopy for the transfer of the mole fraction from the RS to the working standards are developed, in order to reduce the required number of RS and improve the accuracy of measurements. For the successful use of existing spectroscopic databases, the most accurate data was necessary to identify and attribute the uncertainty, based on our own experimental work carried out using the RS. Further on the transfer of the mole fraction from the RS to the working standards can be done without the use of the RS. In the case of CRDS, when the matrix of the studied gas mixture is different from air, the broadening of the spectral lines associated with the interactions between molecules leads to significant error in the measurement of concentration of the studied gas. The effects leveling benefits of the CRDS method are studied

Problems of metrological assurance of gas analysis using IR spectroscopy

The survey article presents the results of work on metrological assurance of measurements using IR spectrometers, IR correlation gas analyzers and CRDS instruments. For the successful application of the existing databases in absorption spectroscopy, it is necessary to identify the most accurate data and assign uncertainty to it, based on experimental studies using reference gas mixtures. The properties of the methods that lead to a deterioration in the measurement accuracy were investigated and the ways were suggested to overcome the shortcomings of the measuring methods

Raman Gas Analyzer of Carbon Isotopologues with 50 ppm Level Sensitivity

International audienc

Purity determination as needed for the realisation of primary standards for elemental determination: status of international comparability

Peer reviewed: YesNRC publication: Ye

International Key Comparison CCQM-K226b and Pilot Study CCQM P50b (S02): Comparison of Primary Standards of Sulphur Dioxide (SO2) in Synthetic Air

Accurate measurements of sulphur dioxide at the concentrations found in ambient air have become essential to support monitoring and legislation concerned with air quality. In general, the primary element of quality assurance for field instruments is regular calibration using certified gas mixtures. The concentration range chosen for this Key Comparison (240 nmol/mol to 320 nmol/mol) is defined by appropriate European standards and is typical of similar levels used around the world. The travelling standards used for the comparison were prepared commercially by a supplier with a proven track record of preparing stable mixtures of the relevant gases. The coordinating laboratory (NPL) carried out stability checks on the mixtures and determined the amount fraction using a primary gravimetric permeation facility. These data were used to determine the drift rate (and uncertainty) of each standard. The results for the 11 participants in CCQM-K26.b and the one participant in CCQM-P50.b are presented in this report. Degrees of equivalence have been calculated based on a reference value (corresponding to the KCRV) derived from the primary gravimetric facility used by the coordinating laboratory.JRC.F.8-Sustainable Transpor

An International Comparability Study to Determine the Sources of Uncertainty Associated with a Non-competitive Sandwich Fluorescent ELISA

Immunoassays allow the specific detection of biological molecules in complex samples at physiologically relevant concentrations. However, there are concerns over the comparability of such techniques when the same assay is performed by different operators or laboratories. an international intercomparison study was performed to assess the uncertainty involved in the estimation of a protein cytokine concentration using a fluorescent ELISA.JRC.D.2-Reference material

CCQM-K102 Polybrominated diphenyl ethers in sediment

The key comparison CCQM-K102: Polybrominated diphenyl ethers in sediment was coordinated by the JRC, Directorate F – Health, Consumers & Reference Materials, Geel (Belgium) under the auspices of the Organic Analysis Working Group (OAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM). Thirtheen National Metrology institutes or Designated Institutes and the JRC participated. Participants were requested to report the mass fraction (on a dry mass basis) of BDE 47, 99 and 153 in the freshwater sediment study material. The sediment originated from a river in Belgium and contained PBDEs (and other pollutants) at levels commonly found in environmental samples. The comparison was designed to demonstrate participants' capability of analysing non-polar organic molecules in abiotic dried matrices (approximate range of molecular weights: 100 to 800 g/mol, polarity corresponding to pKow < -2, range of mass fraction: 1-1000 µg/kg). All participants (except one using ultrasonic extraction) applied Pressurised Liquid Extraction or Soxhlet, while the instrumental analysis was performed with GC-MS/MS, GC-MS or GC-HRMS. Isotope Dilution Mass Spectrometry approach was used for quantification (except in one case). The assigned Key Comparison Reference Values (KCRVs) were the medians of thirteen results for BDE 47 and eleven results for BDE 99 and 153, respectively. BDE 47 was assigned a KCRV of 15.60 µg/kg with a combined standard uncertainty of 0.41 µg/kg, BDE 99 was assigned a KCRV of 33.69 µg/kg with a combined standard uncertainty of 0.81 µg/kg and BDE 153 was assigned a KCRV of 6.28 µg/kg with a combined standard uncertainty of 0.28 µg/kg. The k-factor for the estimation of the expanded uncertainty of the KCRVs was chosen as k = 2. The degree of equivalence (with the KCRV) and its uncertainty were calculated for each result. Most of the participants to CCQM-K102 were able to demonstrate or confirm their capabilities in the analysis of non-polar organic molecules in abiotic dried matrices. Throughout the study it became clear that matrix interferences can influence the accurate quantification of the PBDEs, if the analytical methodology applied is not appropriately adapted and optimised. This comparison shows that quantification of PBDEs at the µg/kg low-middle range in a challenging environmental abiotic dried matrix can be achieved with relative expanded uncertainties below 15 % (more than 70 % of participating laboratories), well in line with the best measurement performances in the environmental analysis field.JRC.F.6-Reference Material