Capabilities Of National Metrology Institutes Research Articles

Final report for SIM.QM-S12: supplementary comparison for trace elements in natural water

Main textThe SIM Supplementary Comparison SIM.QM-S12 for Trace Elements in Natural Water was undertaken to assess and demonstrate the analytical capabilities of national metrology institutes (NMIs) and designated institutes (DIs) of SIM members (or other regions) for the accurate determination of trace elements in natural water at µg/kg levels.Evidence of successful participation in formal, relevant international comparisons is needed to document calibration and measurement capability claims (CMCs) made by NMIs and DIs.Seventeen NMIs and DIs participated. Participants were requested to evaluate the mass fractions, expressed in µg/kg, of arsenic, cadmium, lead and antimony in a natural mineral groundwater that was spiked with the respective elements. A variety of instrumental techniques including inductively coupled plasma mass spectrometry (ICP-MS), isotope dilution ICP-MS (ID-ICP-MS), inductively coupled plasma optical emission spectrometry (ICP-OES), electrothermal atomic absorption spectrometry (ETAAS) and hydride generation flame atomic absorption spectrometry (HG-FAAS) were used by the participants for the determination.The NIST decision tree was used to assign the SCRV estimate for the proposed measurands and to calculate the degrees of equivalence of each national measurement standard following the IAWG Guidance on Using NIST Decision Tree for Comparison Reporting from 30 June 2023.Successful participation in SIM.QM-S12 demonstrates measurement for determination of elements in water matrices. Considering the IAWG Core Capability Matrix, this material falls into the matrix challenge called "Water/aqueous", which corresponds to the CCQM amount-of-substance category fresh water, and so will support CMCs for the metalloids and semi-metals at mass fraction levels below 50 µg/kg (As and Sb measurements) and transition elements at mass fraction levels below 50 µg/kg (except Hg) (for Cd and Pb measurements).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).

Final report of CCQM-K157 for the measurement of the amount of substance of HfO2 expressed as the thickness of nm films

Main textThe key comparison CCQM-K157 for the thickness measurement of HfO2 films was performed by the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The aim of CCQM-K157 is to establish the measurement traceability and to ensure the equivalency in the measurement capability of national metrology institutes for the thickness measurement of HfO2 films.In this key comparison, the thicknesses of six HfO2 films with the nominal thickness range from 0.7 nm to 6 nm were compared by x-ray photoelectron spectroscopy (XPS), x-ray reflectometry (XRR), transmission electron microscopy (TEM), spectroscopic ellipsometry (SE) and medium energy ion scattering spectrometry (MEIS).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).

Test of a digitizer to process the pulse signal from the 3 photomultiplier tubes of a TDCR liquid scintillation counter

The BIPM is developing a new service for international key comparisons in radionuclide metrology. The system, called ESIR, is based on a liquid scintillation counter using the Triple-to-Double Coincidence Ratio (TDCR) technique. The aim is to produce an international reference that can be reproduced over several decades of time in order to compare the calibration capabilities of National Metrology Institutes (NMIs). The maintainability of the electronics performing the signal processing is a challenge. To ensure the long-term sustainability of the electronics, the strategy is to set up redundant systems including at least one digital electronics module. The analogue modules developed in the 1990s and 2000s are less and less maintained and digital electronics are increasingly available on the market. In this context, a digitizer was tested and its suitability for the TDCR measurements compared to the currently used module based on an analogue front-end. This first implementation directly linking the photomultiplier anode to the CAEN digitizer without any analogue preconditioning shows a significant loss of detection efficiency and a lower signal to noise ratio observed on distributions of single photoelectrons. Although the TDCR method can correct for these efficiency losses, the loss of symmetry between the channels is too great to provide a sufficiently robust measurement. The use of low-pass filters upstream of the ADC will be considered to make this digital measurement system more reliable.

International comparison CCQM-K10.2018: BTEX in nitrogen at 5 nmol mol−1

Main textThe CCQM-K10.2018 comparison aimed to evaluate the capabilities of national metrology institutes (NMIs) to prepare and/or value assign primary reference mixtures containing benzene, toluene, ethylbenzene, p-xylene, m-xylene and o-xylene (subsequently referred to as BTEX) in nitrogen. This key comparison was separated into two parallel studies. The first study, deemed the "gravimetric study", evaluated the level of compatibility of BTEX standards provided by NMIs. Seven participating laboratories each submitted one standard at nominal 5 nmol mol-1 BTEX in nitrogen. Comparison measurements were performed by the National Institute of Standards and Technology (NIST) from July to October 2018. The second study, deemed the "comparative study", compared the capabilities of NMIs to measure the amount fractions of BTEX in a mixture provided by NIST. NIST prepared one standard at nominal 5 nmol mol-1 BTEX in nitrogen, which was measured consecutively by three participating laboratories. The participants' measurements took place from August 2018 to March 2019. The comparison protocol adopted for CCQM-K10.2018 was more challenging than for the original comparison, CCQM-K10 in 2001, and the results provide an extended evaluation of the level of compatibility of BTEX in nitrogen standards.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).

SIM.QM-S10: supplementary comparison for trace elements in skim milk powder

Main textSIM.QM-S10 was performed to assess the analytical capabilities of National Metrology Institutes (NMIs) and Designated Institutes (DIs) of SIM members (or other regions) for the accurate determination of trace metals in skim milk powder. The study was proposed by the coordinating laboratories National Research Council Canada (NRC) and INTI Argentina as an activity of Sistema Interamericano de Metrología (SIM) approved by the Inorganic Analysis Working Group (IAWG) of Consultative Committee for Amount of Substance - Metrology in Chemistry and Biology (CCQM). Participants included NMIs/DIs from twelve countries. No measurement method was prescribed by the coordinating laboratories. Therefore, NMIs used measurement methods of their choice. However, the majority of NMIs/DIs used closed vessel microwave system using a mixture of HNO3 and H2O2 for the digestion and ICP-MS and ICP-OES for the determination of the measurands. One laboratory used INAA technique.This SIM.QM-S10 Supplementary Comparison provides NMIs/DIs with the needed evidence for CMC claims for trace elements in skim milk powder and similar matrices.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).

Thickness measurement of nm HfO2 films

Main textA pilot study for the thickness measurement of HfO2 films was performed by the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The aim of this pilot study was to ensure the equivalency in the measurement capability of national metrology institutes for the thickness measurement of HfO2 films. In this pilot study, the thicknesses of six HfO2 films with nominal thickness from 1 nm to 4 nm were measured by X-ray Photoelectron Spectroscopy (XPS), X-ray Reflectometry(XRR), X-ray Fluorescence Analysis (XRF), Transmission Electron Spectroscopy (TEM), Spectroscopic Ellipsometry (SE) and Rutherford Backscattering Spectrometry (RBS). The reference thicknesses were determined by mutual calibration of a zero-offset method (Medium Energy Ion Scattering Spectroscopy (MEIS) of KRISS) and a method traceable to the length unit (the average thicknesses of three XRR data except the thinnest film). These reference thicknesses are traceable to the length unit because they are based on the traceability of XRR. For the thickness measurement by XPS, the effective attenuation length of Hf 4f electrons was determined. In the cases of XRR and TEM, the offset values were determined from a linear fitting between the reference thicknesses and the individual data by XRR and TEM. The amount of substance of HfO2, expressed as thickness of HfO2 films (in both linear and areal density units), was found to be a good subject for a CCQM key comparison.To reach the main text of this paper, click on Final Report. The final report has been peer-reviewed and approved for publication by the CCQM.

An insight into the present capabilities of national metrology institutes for measuring sparkle

Large-effect pigments, due to their strongly specular reflectance, produce a special visual texture known as sparkle. The use of these pigments in many industries (automotive, cosmetic, paper, architecture...) makes the control of this visual texture necessary. Sparkle measurands have been defined in this article, so that traceability of sparkle measurements can be provided by national metrology institutes or designated institutes. Some of them (Physikalisch-Technische Bundesanstalt, Eidgenössisches Institut für Metrologie, Cesky Metrologicky Institut and Consejo Superior de Investigaciones Científicas) have tested their existing measurement capabilities for the defined sparkle measurands, and their results are presented and thoroughly compared. Two possible sources of systematic error have been identified: inadequate illumination and collection solid angles, and an inadequate size of the virtual aperture used to assess the luminous flux reflected by the effect pigments. Finally, it has been shown that the measures correlate excellently with the sparkle visual data. The results shown in this research support the sparkle measurands defined here as adequate quantities for defining the standard measurement scale of sparkle claimed by industry.

Main results of GULFMET.EM-S5/5.1 supplementary comparisons for electrical energy at frequencies of 50/53 Hz

International agreements are the basis for establishing global metrological traceability. The Arrangement on the Mutual Recognition of National Standards, Calibration and Measurement Capabilities of National Metrology Institutes (NMIs) of the International Committee for Weights and Measures plays a key role in ensuring the international equivalence of national standards in different countries. The main basis of this arrangement is specific guidelines and recommendations, in particular for the comparison of standards.Regional metrology organisations (RMOs) traditionally carry out both key and supplementary comparisons of national standards of the unit of electric power at frequencies of 50 and 53 Hz, in particular within the framework of COOMET, the pilot laboratory of which was SE “Ukrmetrteststandard”. However, supplementary comparison of the national standards at frequencies of 50 and 60 Hz for energy units was conducted only by the RMOs of the American continent – SIM.The article presents the main results of international supplementary comparisons of national standards of active and reactive electrical energy units at frequencies of 50 and 53 Hz within the framework of the GULFMET.EM-S5 and GULFMET.EM-S5.1 project. Comparisons piloted by the SE “Ukrmetrteststandard” were conducted radially with the participation of the National Metrological Institutes of Ukraine, Turkey and the United Arab Emirates (UAE) during 2019 and 2020.The drift of the travelling standard was estimated over the entire period of the comparison and was small for all measurement points. The degree of equivalence of national standards active and reactive energy for power factors of 1.0, 0.5 Lag and 0.5 Lead has been established. Results of estimation of consistency of the received data are presented. Values number En for all NMIs for all measuring points meet the set requirements. Linked results of GULFMET.EM-S5 and GULFMET.EM-S5.1 supplementary comparisons were presented.

Final report of the SIM.QM-S7 supplementary comparison, trace metals in drinking water

SIM.QM-S7 was performed to assess the analytical capabilities of National Metrology Institutes (NMIs) and Designated Institutes (DIs) of SIM members (or other regions) for the accurate determination of trace metals in drinking water. The study was proposed by the coordinating laboratories National Research Council Canada (NRC) and Centro Nacional de Metrologia (CENAM) as an activity of Inorganic Analysis Working Group (IAWG) of Consultative Committee for Amount of Substance - Metrology in Chemistry and Biology (CCQM). Participants included 16 NMIs/DIs from 15 countries. No measurement method was prescribed by the coordinating laboratories. Therefore, NMIs used measurement methods of their choice. However, the majority of NMIs/DIs used ICP-MS.This SIM.QM-S7 Supplementary Comparison provides NMIs/DIs with the needed evidence for CMC claims for trace elements in fresh waters and similar matrices.Main textTo 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).

Final report of the key comparison CCQM-K72: Purity of zinc with respect to six defined metallic analytes

High purity elements can serve as a realization of the SI unit amount of substance for the specific element. Solutions prepared from high purity metals by applying gravimetric preparation and the concept of molar mass are used as 'calibration' solutions in many fields of analytical chemistry and provide the metrological basis in elemental analysis. Since ideal purity does not exist for real materials, the actual purity of the high purity material must be known with a specified uncertainty. As required uncertainties around 10−4 relative on the purity statement are not accessible in almost all cases by a direct measurement of the element in itself, the indirect approach is followed, where all elements excepting the matrix element itself are measured and their sum is subtracted from the value for ideal purity, which is 1 kg/kg.It was the aim of this comparison to demonstrate the capability of national metrology institutes and designated institutes to determine the purity of pure elements. In order to limit the effort within this comparison, only six metallic impurities (Ag, Al, Cd, Cr, Ni, Tl) in the low mg/kg range are considered in a zinc matrix. It has to be underlined here that the task was to measure the purity of zinc based on the determination of six analytes. The task is not trace analysis of specific analytes in zinc. This subtle distinction defines different measurands.The sample, pure Zn, was cut in pieces of cubic geometry for wet chemical analysis or of pin geometry for GDMS analysis and was sent to the participants. The comparison was run under the auspices of the Inorganic analysis Working Group (IAWG) of the CCQM and was piloted by the BAM Federal Institute for Materials Research and Testing, Berlin, Germany. The majority of the participants applied ICP-MS techniques and only two participants used additionally atomic absorption spectrometry. GDMS was used only by one participant.The observed spreads for the measurement results reported by the participants were significantly lower than those of the preceding study CCQM-P107 and were well below the target uncertainty of 30% relative. As a consequence, comparability within the participating laboratories is demonstrated to be established. The individual measurement results, mean values and medians derived were in all cases very consistent with the reference values obtained by IDMS and so the accuracy of the measurement results for the participating laboratories is as well demonstrated to be established. Especially with the results of CCQM-P62 and CCQM-P107 in mind, the outcome of CCQM-K72 can be considered as a big step forward in the community.CCQM is aware of the difference between a characterization based on only six analytes and a complete characterization. Therefore, the pilot study CCQM-P149 has been initiated and already started, which focuses on the fit-for-purpose approaches for the purity determination of metals (here: zinc) to be used as primary standards in elemental analysis. Another follow-up in the form of a pilot study on non-metal impurities is mandatory, because non-metal impurities such as oxygen, nitrogen and sulfur often make up the largest contributions.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).

Measurements and data of thermophysical properties traceable to a metrological standard

In order to improve the performance of devices, components and systems, where heat is generated, transported, stored or converted to other types of energy, reliable thermal design and simulation are required using reliable thermophysical property data. In order to produce reliable thermophysical property data systematically and continually, the international and national standards of thermophysical properties must be established and the measurement methods should be evaluated and standardized, and the measuring instruments must be calibrated by reference materials traceable to the international or national standard.Users search for and purchase a particular grade of material which satisfies the properties, performances and technical specifications required. In order to guarantee fair commerce and trade, values of thermophysical properties should be measured traceable to the national standard. Thus, the establishment of an international standard is required satisfying the global CIPM MRA under the metric convention, and then, the global and regional framework to examine calibration and measurement capability of national metrology institutes (NMIs). A domestic traceability system in each country should be established and the quality management system of the NMI and calibration laboratories should be constructed based on ISO 17025.

Final report on Key Comparison K67 and parallel Pilot Study P108: Measurement of composition of a thin Fe–Ni alloy film

The Key Comparison K67 and the parallel Pilot Study P108 on quantitative analysis of thin alloy films have been completed in the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The aim of these inter-laboratory comparisons is to determine the degree of equivalence in the measurement capability of national metrology institutes (NMIs) and designated institutes (DIs) for the determination of the composition of thin alloy films. The measurand is expressed in atomic percent. A Fe–Ni alloy film with a certified composition was available for the participants of the inter-laboratory comparison. It has been used as a reference specimen to determine the relative sensitivity factors (RSF) of Fe and Ni for the different analytical methods used by the participants to determine the composition of the test sample. As was shown in the preceding Pilot Study P98, the degrees of equivalence in the measurement capabilities of the participants can be improved in that way. The composition of the reference specimen was certified by inductively coupled plasma mass spectrometry (ICP-MS) using the isotope dilution method. The in-depth and lateral homogeneity, determined in terms of elemental composition, of the certified reference sample and the unknown test sample were confirmed by secondary ion mass spectrometry (SIMS) using C60 primary ions by the leading laboratory. Five laboratories participated in the key comparison. Four of them used x-ray photoelectron spectroscopy (XPS) and one Auger electron spectroscopy (AES). One laboratory participated in the parallel P108 pilot study using electron probe micro analysis with an energy-dispersive spectrometer (ED EPMA) and XPS.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).

Final report on international comparison CCQM-K71: Measurement of stack gas

Industrial stack gas emission measurements are important for process control, control of air pollution, and for implementing legislation regarding carbon dioxide emission rights. Measurements are typically performed using a range of process analysers for carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx), sulphur dioxide (SO2) and miscellaneous hydrocarbons. The calibration of these analysers is often performed using a series of binary mixtures of each component in nitrogen. For reasons of efficiency as well as a better match with true stack gas, the use of multi-component mixtures for this purpose would be preferred.The aim of this key comparison is to evaluate the measurement capabilities of national metrology institutes for carbon monoxide, carbon dioxide, nitrogen monoxide, sulphur dioxide and propane in nitrogen. Ten laboratories participated in the key comparison and one in the associated study. The key comparison reference value is based on the gravimetric preparation data.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).

Key comparison CCQM-K60: Total selenium and selenomethionine in selenised wheat flour

Key comparison CCQM-K60 was performed to assess the analytical capabilities of national metrology institutes (NMIs) to accurately quantitate the mass fraction of selenomethionine (SeMet) and total selenium (at low mg kg−1 levels) in selenised wheat flour. It was organized by the Inorganic Analysis Working Group (IAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM) as a follow-up key comparison to the previous pilot study CCQM-P86 on selenised yeast tablets. LGC Limited (Teddington, UK) and the Institute for National Measurement Standards, National Research Council Canada (NRCC, Ottawa, Canada) acted as the coordinating laboratories. CCQM-K60 was organized in parallel with a pilot study (CCQM-P86.1) involving not only NMIs but also expert laboratories worldwide, thus enabling them to assess their capabilities, discover problems and learn how to modify analytical procedures accordingly.Nine results for total Se and four results for SeMet were reported by the participant NMIs. Methods used for sample preparation were microwave assisted acid digestion for total Se and multiple-step enzymatic hydrolysis and hydrolysis with methanesulfonic acid for SeMet. For total Se, detection techniques included inductively coupled plasma mass spectrometry (ICP-MS) with external calibration, standard additions or isotope dilution analysis (IDMS); instrumental neutron activation analysis (INAA); and graphite furnace atomic absorption spectrometry (GFAAS) with external calibration. For determination of SeMet in the wheat flour sample, the four NMIs relied upon measurements using species-specific IDMS (using 76Se-enriched SeMet) with HPLC-ICP-MS.Eight of the nine participating NMIs reported results for total Se within 3.5% deviation from the key comparison reference value (KCRV). For SeMet, the four participating NMIs reported results within 3.2% deviation from the KCRV. This shows that the performance of the majority of the CCQM-K60 participants was very good, illustrating their ability to obtain accurate results for such analytes in a complex food matrix containing approximately 17 mg kg−1 Se.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).

International framework of traceability for radiation dosimetry quantities

An overview of the international framework that supports the dissemination of the dosimetry quantities for ionizing radiation is presented. The aim of international traceability is for confidence in such measurements around the world, which is particularly important for the equivalence of patient treatment regimes as required in international clinical trials for radiotherapy but also for fields as diverse as industrial processing, diagnostic medicine and radiation protection. This paper gives some explanation of the comparison system for national primary standards in the field of dosimetry and shows how these can support the claims for the calibration and measurement capabilities of national metrology institutes represented in the BIPM key comparison database.

Report of the study CCQM-K64: Analysis of a copper alloy

The CCQM-K64 study was performed to demonstrate and document the measurement capabilities of national metrology institutes in the determination of main and minor elements in copper alloys. The key comparison was coordinated by BAM Federal Institute for Materials Research and Testing, Berlin, Germany as an activity of the Inorganic Analysis Working Group of CCQM. Elements to be determined were Cu, Pb, Sn, Fe and Ni in a lead-containing brass. Five national metrology institutes registered to participate in CCQM-K64. Three of them analysed all five elements requested, two of them did not perform analyses for tin. The participants used different analytical methods: all of them seem to be suitable, especially for Cu determination.The BAM reference material AKP 220/2 Special Brass (unknown to the participants) was used as a test sample in this study.CCQM-K64 demonstrates the abilities of metrological institutes to measure the mass fractions of main, minor and trace components of a copper alloy for copper (main element, >50% mass fraction), lead (minor element, 1% to 5% mass fraction) and iron, nickel and, with reservations, tin (as trace components, 0.01% to 0.5% mass fraction). Only three of the five participants determined tin.The analytical methods used were electrogravimetry (for copper and lead), flame-AAS and ICP-MS.The scope of the key comparison extends to other copper alloys comprising the same or similar constituents and other elements in the same mass fraction range when analysed using the technique(s) applied in CCQM-64. It extends also to other non-ferrous metal alloys if the sample preparation is similar.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).

Report on CCQM-P98: Quantitative analysis of thin Fe–Ni alloy films using a certified alloy reference material for calibration of testing methods

The pilot study P98 on quantitative surface analysis of alloy films was performed by the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The aim of this pilot study is to ensure the equivalency in the measurement capability of national metrology institutes (NMIs) for the quantification of thin alloy films. Nine laboratories including five NMIs, three companies and one university participated in this pilot study. The majority of the participants used x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), which are useful methods for the quantitative analysis of thin alloy films or structured surfaces made of them. The compositions of the certified reference material and the other test samples were determined by inductively coupled plasma mass spectrometry (ICP-MS) using the isotope dilution method. The in-depth and lateral homogeneities of the composition were confirmed by secondary ion mass spectrometry (SIMS) using a C60 ion source.In this pilot study, the quantification of Fe–Ni alloy films has been proven to be a good candidate as a subject for a CCQM key comparison. The measured slope and offset values of participants' XPS, AES or EPMA data versus compositions obtained by ICP-MS are considered in detail. Data sets for the compositions obtained either by relative sensitivity factors (RSFs) determined from (a) pure metal films or by RSFs from (b) a certified reference alloy film are compared with the result that the average offset value is substantially reduced from 0.725 to 0.038 for the Fe51–Ni49 alloy film test sample. This result means that the RSFs obtained from an alloy film are much more appropriate than those RSFs from pure metals for the quantification of alloy films because a matrix effect can be successfully covered in the first case. This is the right way to improve the equivalency in the measurement capabilities of participants. Similar results have been observed in an analysis of data obtained with the Fe28–Ni72 and Fe78–Ni22 test films. The compositions measured by XPS using RSFs determined from an alloy film showed the minimum in deviation from the nominal values.Main text.To reach the main text of this paper, click on Final Report.The final report has been peer-reviewed and approved for publication by the CCQM Working Group on Surface Analysis.

Analysis of a copper alloy: Comité Consultatif pour la Quantite de Matière (CCQM) pilot study P76 international intercomparison

The capabilities of National Metrology Institutes (NMIs) and selected outside “expert” laboratories of determining the mass fractions of the main and minor elements Cu, Pb, Sn, Fe, and Ni in a lead-containing brass were assessed. This pilot study P76 was organized as an activity of the Inorganic Analysis Working Group of CCQM and was piloted by the Federal Institute for Materials Research and Testing (BAM). In total 12 laboratories (four NMIs and eight outside labs) submitted results, some of them more than one set of results per element. The laboratories were free to choose any analytical method they wanted to use for the analysis. Consequently various methods of measurement were employed: inductively coupled plasma optical emission spectrometry (ICP–OES), inductively coupled plasma mass spectrometry (ICP–MS), instrumental neutron-activation analysis (INAA), titrimetry, flame atomic-absorption spectrometry (FAAS), spectrophotometry (MAS), electrogravimetry, and gravimetric analysis. After testing for homogeneity within BAM, a certified reference material of lead-containing brass was used as test sample without informing the participants about the source of the material. The agreement of the results for all elements investigated was acceptable and mean values calculated from the results of all participants were close to the certified mass fractions of the CRM used as test sample. No statistically significant differences between the results of the NMIs and those of the non-NMIs could be observed.

Total selenium and selenomethionine in pharmaceutical yeast tablets: assessment of the state of the art of measurement capabilities through international intercomparison CCQM-P86

Results of an international intercomparison study (CCQM-P86) to assess the analytical capabilities of national metrology institutes (NMIs) and selected expert laboratories worldwide to accurately quantitate the mass fraction of selenomethionine (SeMet) and total Se in pharmaceutical tablets of selenised-yeast supplements (produced by Pharma Nord, Denmark) are presented. The study, jointly coordinated by LGC Ltd., UK, and the Institute for National Measurement Standards, National Research Council of Canada (NRCC), was conducted under the auspices of the Comité Consultatif pour la Quantité de Matière (CCQM) Inorganic Analysis Working Group and involved 15 laboratories (from 12 countries), of which ten were NMIs. Apart from a protocol for determination of moisture content and the provision of the certified reference material (CRM) SELM-1 to be used as the quality control sample, no sample preparation/extraction method was prescribed. A variety of approaches was thus used, including single-step and multiple-step enzymatic hydrolysis, enzymatic probe sonication and hydrolysis with methanesulfonic acid for SeMet, as well as microwave-assisted acid digestion and enzymatic probe sonication for total Se. For total Se, detection techniques included inductively coupled plasma (ICP) mass spectrometry (MS) with external calibration, standard additions or isotope dilution MS (IDMS), inductively coupled plasma optical emission spectrometry , flame atomic absorption spectrometry and instrumental neutron activation analysis. For determination of SeMet in the tablets, five NMIs and three academic/institute laboratories (of a total of five) relied upon measurements using IDMS. For species-specific IDMS measurements, an isotopically enriched standard of SeMet (76Se-enriched SeMet) was made available. A novel aspect of this study relies on the approach used to distinguish any errors which arise during analysis of a SeMet calibration solution from those which occur during analysis of the matrix. To help those participants undertaking SeMet analysis to do this, a blind sample in the form of a standard solution of natural abundance SeMet in 0.1 M HCl (with an expected value of 956 mg kg(-1) SeMet) was provided. Both high-performance liquid chromatography (HPLC)-ICP-MS or gas chromatography (GC)-ICP-MS and GC-MS techniques were used for quantitation of SeMet. Several advances in analytical methods for determination of SeMet were identified, including the combined use of double IDMS with HPLC-ICP-MS following extraction with methanesulfonic acid and simplified two-step enzymatic hydrolysis with protease/lipase/driselase followed by HPLC-ICP-IDMS, both using a species-specific IDMS approach. Overall, satisfactory agreement amongst participants was achieved; results averaged 337.6 mg kg(-1) (n = 13, with a standard deviation of 9.7 mg kg(-1)) and 561.5 mg kg(-1) (n = 11, with a standard deviation of 44.3 mg kg(-1)) with median values of 337.6 and 575.0 mg kg(-1) for total Se and SeMet, respectively. Recovery of SeMet from SELM-1 averaged 95.0% (n = 9). The ability of NMIs and expert laboratories worldwide to deliver accurate results for total Se and SeMet in such materials (selensied-yeast tablets containing approximately 300 mg kg(-1) Se) with 10% expanded uncertainty was demonstrated. The problems addressed in achieving accurate quantitation of SeMet in this product are representative of those encountered with a wide range of organometallic species in a number of common matrices.

International comparison CCQM-P41 Greenhouse gases. 1. Measurement capability

The measurement of greenhouse gases in the atmosphere is one of the activities to monitor changes in the global environment, as some of these gases are presumed to contribute to climate change. The CCQM Gas Analysis Working Group has organised a pilot comparison for carbon dioxide and methane at ambient levels to compare primarily the capabilities of national metrology institutes (NMIs) for measuring these species in air. The participation in this comparison was not limited to signatories of the MRA, as is usually the case. Laboratories from the World Meteorological Organisation (WMO) were invited as well, and two participated.The project has been split in two parts, a comparison of the (analytical) measurement capability, and a high-accuracy comparison of primary standard gas mixtures for greenhouse gases. In this first part, the measurement capability was compared between NMIs and WMO laboratories. The nominal amount-of-substance fraction levels are 365 µmol/mol for carbon dioxide and 1.8 µmol/mol for methane. The matrix was synthetic air, simulated by a mixture of nitrogen, oxygen (209 mmol/mol) and argon (9.3 mmol/mol). The measurements took place in the spring of 2003.The protocol used for this comparison was the same as used so far in the gas analysis area for key comparisons and studies of this type. The reference values were assigned to each gas mixture on the basis of the gravimetric preparation, taking into account the results from the purity verification. In particular for the value assignment of methane, traces of methane in the matrix gases (nitrogen, oxygen and argon) can influence the value assigned to the gas mixture appreciably.The results for methane agree within 4% relative, and for most participants even within 2% relative at an amount of substance fraction level of 1.8 µmol/mol. For carbon dioxide all results agree within 1% relative, and for most the agreement is even better: within 0.5% relative at an amount of substance fraction level of 365 µmol/mol. The methane data show a discrepancy of approximately 0.025 µmol/mol between the averages of the WMO laboratories and the NMIs, which confirms results of earlier comparisons. Measurement traceability is quite differently established in NMIs and WMO laboratories, and may account for this difference. Further work is needed to find out the causes of this difference.Main text.To reach the main text of this paper, click on Final Report.The final report has been peer-reviewed and approved for publication by the CCQM.