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Due to recent advances in technical developments of NMR instruments such as acquisition electronics and probe design, detection limits of components in liquid mixtures were improved into the lower ppm range (approx. 5–10 ppm amount of substance). This showed that modern NMR equipment is also suitable for the observation of hydrocarbon samples in the expanded fluid phase or gas phase. Since Quantitative NMR spectroscopy (qNMR) is a direct ratio method of analysis without the need of calibration it was used to determine impurities in appropriate liquid and liquefied hydrocarbon isomers up to C6, which are used for preparation of primary gas standards, e.g., natural gas or exhaust gas standards. At the same time it is possible to yield structural information with a minimum of sample preparation. Thus, cross contaminations between different isomers of the observed hydrocarbons and their (NMR-active) impurities can be identified and quantified.
In general, most quantitative organic chemical measurements rely on the availability of highly purified compounds to act as calibration standards. The traceability and providence of these standards is an essential component of any measurement uncertainty budget and provides the final link of the result to the units of measurement, ideally the SI. The more recent increase in the use of qNMR for the direct assessment of chemical purity however can potentially improve the traceability and reduce the uncertainty of the measured chemical purity at a reduced cost and with less material. For example the method has beneficially been used by National Measurement institutes for recent CCQM comparisons including the CCQM–K55 series of purity studies.
Traditional ‘indirect’ methods of purity analysis require that all impurities are identified and quantified, leading to a minimum of 4 individual analytical methods (organic impurities, water, solvents, inorganic residue). These multiple technique approaches measure an array of different chemical impurities normally present in purified organic chemical compounds. As many analytical methodologies have compound-specific response factors, the accuracy and traceability of the purity assessment is dependent on the availability of reference materials of the impurities being available.
qNMR provides the most universally applicable form of direct purity determination without need for reference materials of impurities or the calculation of response factors but only exhibiting suitable NMR properties. The development of CRMs addressing qNMR specific measurement issues will give analysts compounds ideally suited for the analytical method and also provide full characterisation of qNMR related parameters to enable more realistic uncertainty budgets. These materials will give users the tools to exploit qNMR more easily and enable them to speed up analytical method development and reduce the time and financial burden of multiple analytical testing.
Purity statements of high purity materials serving as primary standards by GDMS.
Primary standards are materials known for their total purity and therefore appropriate to realise the link with the International System of Units (SI). The realisation and dissemination of primary standards is of fundamental importance for comparability of measurement results through traceability in all fields of chemical analysis.
To serve as a primary standard for element determination the total purity of a high purity material needs to be measured. In order to achieve a sufficiently small uncertainty (i.e. < 0.01%) this involves determining all possible impurity contributions and to subtract their sum from the ideal purity of 100%.
GD-MS has the potential to reduce the effort for purity determination, as a fast sensitive multi-element analysis without extensive sample preparation. Similar to other solid sampling techniques, glow discharge
requires calibration link the measured signal and the content of the impurities in the matrix.
The use of the concept Relative Sensitivity Factors (RSFs) provides good approximations especially for high purity materials. However, it only works with a wide uncertainty of the results.
The preparation of synthetic pressed powder samples by different modifications of liquid and powder doping used for the determination of both metallic and none-metallic impurities are described. Efficient determination of metallic impurities by GD-MS via differential and absolute measurements with a significantly reduced target uncertainty of 20 % for absolute measurements using liquid doped pressed powder calibration could be achieved. The determination of impurities has been evaluated by independent analytical methods such as HR-ICP-MS, ETAAS; CGHE and combustion analysis
CCQM has established a framework of comparisons to demonstrate the international comparability of chemical measurements. The key point is the establishment of comparable measurements, with traceability to internationally or nationally stated references. The Surface Analysis Working Group (SAWG) has been formally founded in 2003. CCQM ratified the group as a full working group of CCQM in April 2003 with these terms of reference:
- to develop pilot studies and carry out key comparisons of national measurement standards for surface and micro/nano-analysis;
- to assist in identifying and establishing inter-laboratory work to improve the traceability of surface and micro/nano-analysis;
- to establish and update a work plan to be adopted by CCQM;
- to discuss and review the scope of the working group and to liase with other working groups related to nanotechnology.
Following the 2015 meeting of the CCQM, the pilot study CCQM-P130 “WD and ED Electron Probe Micro Analysis on Au-Cu alloys” lead by BAM&NIST has been finalized. The Key Comparison K-129 “Measurement of atomic fractions in Cu(In,Ga)Se2 Films” lead by KRISS has made substantial progress and is about to be finalized. The new Key Comparison K-136 on “BET specific surface of ” lead by UNIIM&BAM has made strong progress in 2015 and will be finished in 2016.
Ellipsometry is a valuable surface analysis tool with an unmatched sensitivity towards surface layer properties. In this presentation, an initiative is discussed to make ellipsometry also a metrological tool. This is usually seen as very difficult due to the model-based nature of the analysis process. By establishing standardisation and reference materials, ellipsometry can be made traceable and can also become a valuable part of the traceable thin film metrology landscape. This is important because this technique has much potential to determine complex material parameters much needed in the production of high-tech products.
CCQM has established a framework of comparisons to demonstrate the international comparability of chemical measurements. The key point is the establishment of comparable measurements, with traceability to internationally or nationally stated references.
Originally initiated by Dr Martin P Seah, NPL, the Surface Analysis Working Group (SAWG) has been formally founded in 2003. The following terms of reference were presented to CCQM in April 2002. CCQM ratified the group as a full working group of CCQM in April 2003 with these terms of reference:
- to develop pilot studies and carry out key comparisons of national measurement standards for surface and micro/nano-analysis;
- to assist in identifying and establishing inter-laboratory work to improve the traceability of surface and micro/nano-analysis;
- to establish and update a work plan to be adopted by CCQM;
- to discuss and review the scope of the working group and to liase with other working groups related to nanotechnology.
Following the 2016 meeting, the Key Comparison K-129 "Measurement of atomic fractions in Cu(In,Ga)Se2 Films" lead by KRISS and the Key Comparison K-136 on "BET specific surface area of nanoporous Al2O3" lead by UNIIM&BAM have been finished in 2016.
The 15th meeting of SAWG will focus on
- survey on CMC claim submitted with reference to K-129 and K-136.
- the overall and SAWG specific aspects of the CCQM Strategy process,
- a joint meeting with the Inorganic Working Group addressing number concentrations of nano particles,
- discussion of future comparisons.
High purity materials can serve as a realisation of the Système International d’Unitès (SI) unit amount of substance for the specific element. Solutions prepared from such high purity materials using gravimetric preparation and the concept of molar mass are used as calibration solutions in many fields of analytical chemistry. Calibration solutions prepared this way provide the traceability to the SI and are the metrological basis in elemental analysis.
The preparation and characterization of such primary pure substances, representing the realisation of the SI unit amount of substance, is undertaken only by a small number of National Metrology Institutes (NMI) and Designated Institutes (DI).
Many other NMIs and DIs, however, prepare elemental calibration solutions as calibrants for their measurement services, such as the certification of matrix Reference Materials or the provision of reference values for Proficiency Testing schemes. The elemental calibration solutions used for this purpose are not a direct service to customers, such as preparing secondary calibration solutions, but provide the source of traceability for the other services. Hence, it is necessary for the NMI or DI to obtain data on the purity of the pure metals or other materials used to prepare the solutions with measurement uncertainties meeting the needs of the above described services. This is commonly undertaken as a “fit for purpose” assessment, appropriate for the uncertainty requirement of the service provided to customers.
As a consequence, total purity measurements are a long-term strategy of CCQM-IAWG. Several studies were conducted (CCQM-P107, CCQM-K72 and CCQM-P149) on the measurement of the purity of zinc. From these studies, several conclusions can be drawn for the purity assessment of a pure (metallic) element. These conclusions will be put together in this document in order to assist all NMIs/DIs in performing a purity assessment, whenever needed.
The press conference on the results of the European Project FP7 constitutes a dissemination event dedicated to the production and characterization of "Shape-engineered TiO2 nanoparticles for metrology of functional properties: setting design rules from material synthesis to nanostructured devices" with the main large-scale applications in the three reference sectors: energy, health and environment.