Eurachem Newsletter No 11 Winter 1996/97

The EURACHEM Report (4 reports)

Eurachem Reports
  1. Workshop Report: Traceability of "Amount of Substance" Measurements
  2. Report from EURACHEM Education and Training Working Group
  3. IMEP6 Soon to be Evaluated
  4. VIEWPOINT: The use of expiry dates for Chemicals & Reagents

Workshop Report
Traceability of "Amount of Substance" Measurements

A EURACHEM/CITAC Workshop held in Noordwijkerhout, The Netherlands, September 4-6, 1996

EURCHEM held its first workshop on traceability in 1992. A great deal of progress has taken place since that date, much of it within international networking groups such as EURACHEM, CITAC and CCQM. We cannot claim to have even completed the design, let alone built an international chemical measurement system. However, we have in come circles at least, an emerging consensus about the key issues, a skeletal framework and some of the building blocks.

the workshop was organised on behalf of CITAC and EURACHEM by the Laboratory of the Government Chemist. A full report of the proceedings has been submitted for publication.

The aims of the workshop were:

  • To promote mutual understanding between delegates
  • To review progress on the realization of traceability of chemical measurements
  • To further clarify underpinning concepts and terminology leading to the development of a comprehensive model for the traceability of chemical measurements
  • To provide guidance on the tasks we need to undertake to make the traceability of chemical measurements a reality

As well as being alongside the ILAC meeting, scheduled for the following week, the meeting was designed to engineer close cooperation between the laboratory and accreditation communities.

The workshop was a great success with delegates from 23 countries and many organisations. Delegates came from many backgrounds including industry, government laboratories, metrology institutes, academe and accreditation bodies.

Workshop Programme

Workshop activities included scene setting presentations covering:
Traceability to SI P De Bièvre (IRMM)
CCQM: Providing a Firm Foundation R Kaarls (NMi)
Uncertainty: A Key to Traceability W Wegscheider (UMML)
Bridging the Cultural Gap B King (LGC)
What are Primary Methods? W Richter (PTB)
The Role of Reference Materials W Reed (NIST)
Moving from Official to Traceable Methods M Walsh (SLI)
Traceable Measurements at the Working Level A Squirrell (NATA)

The presentations provoked some lively discussion and pumped primed deliberations.These overspilled into Syndicate Task Group discusions which looked at the issues in more detail. Topics under discussion were

Task 1 "What does traceability to the mole really mean?"

  • The equivalence of national measurement standards
  • Definitions and terminology
  • Elemental and organic analysis

Task 2 "How can traceability be realised?"

  • The 'top' of the traceability chain
  • Traceability at the working level
  • The role of reference materials
  • Method dependent analysis

Syndicate groups reported their conclusions at plenary sessions and the workshop ended with a session that brought all the statements together into a set of recommendations and conclusions. Not surprisingly there were some areas of agreement and some areas where confusion and disagreement still reign.

Areas of Agreement

It was pleasing to see the progress that has been made in recent years and to observe that there is a high level of agreement on the following issues:

  1. Traceability is a useful concept that can be applied to chemical measurement
  2. Traceability can be claimed to either SI or to references such as standard methods
  3. Measurement uncertainty is a key concept of traceability and provides a quantitative measure of the quality of measurement data
  4. Further work is required to develop the metrology of chemical measurements, and demonstrator projects, which illustrate the actual benefits are urgently required
  5. CCQM provides the means for establishing a high level international metrology system for chemistry
  6. CITAC and regional networks such as EURACHEM were seen as the keys to providing the second level of metrology support
  7. Most attention needs to be focused on the major problem areas and these include sampling and sample preparation/separation
  8. Reference materials provide a useful aid to traceability by facilitating both calibration and validation processes
  9. A small number of well chosen primary or reference methods and reference materials can be expected to provide a firm basis for traceability to SI and these references can be expected to support working level measurements

Lost in the Fog

Issues where confusion and disagreement still exist include:

  1. What constitutes primary methods and primary reference materials
  2. The applicability of the metrological model employed for physical measurements such as mass, length and time. Is chemical measurement inherently more complex than physical measurement?
  3. The value of the SI unit the mole and how to encourage analytical chemists to use their quantity and unit
  4. Where does traceability start and end? For example, does it include sampling?
  5. How can all the pieces of the jigsaw be fitted together. Is the "virtual metrology laboratory" the way forward?
  6. How can measurement uncertainty be best communicated to the customer without undermining confidence in analytical chemistry?


It was clear that a good level of progress was being made on a number of issues and by a number of groups. The Workshop achieved its aims and provided networking groups such as EURACHEM with valuable material to guide their future work programmes.



Cooperation on International Traceability in Analytical Chemistry
Comité Consultatif pour la Quantité de Matière


  1. B King, submitted to Accreditation Quality Assurance.

    Eurachem Reports

    EURACHEM Education and Training Working Group

    Active Feedback Sought for the Glossary of Analytical Terms

    Analytical data play a vital part in our daily lives, with increasing influence on both economy and ecology. The harmonisation of the European market - including the Eastern European countries - and the opening of international borders for trade and communication have led to serious problems with terminology in analytical chemistry. We can identify the three main reasons which have caused this situation. These can be classified as "linguistics", "semantics", and "acceptance".

    Frequent translations of a term through a chain of languages, and the use of terms by non-native speakers, may lead to a misuse of terms followed by grave misunderstandings. In addition, the coexistence of different meanings of terms due to their independent definition by national and international bodies or authorities, together with recommendations given by international organisations like IUPAC, leads to problems of semantics and confusion resulting in a decrease of acceptance.


    During the last five years, the EURACHEM Education & Training Working Group (E&T WG) has analysed this situation, and has developed a strategy to deal with it. The first, and most important, step of this concept is to provide a forum which initiates and enables international discussions to take place among the experts in the field. The catalyst for these discussions will be a dictionary-like "glossary of terms" which will be published as a series in Accreditation and Quality Assurance. Each term of the glossary is provided with a definition (taken from the highest international level, if possible ISO) followed by a scientific description of the meaning of the definition and one or more examples which explain its practical use. In addition, translations of the term into other European languages will be given. This structure will facilitate translation of the glossary into other languages, and errors will be minimised if not excluded. The translation will be performed by the E & T WG-members, being experts in the field and native speakers of their respective language. Finally it will be published in a suitable national journal.

    Active feedback will be sought at both the national and international levels, to enable a dynamic development of the glossary on the highest possible scientific and linguistic levels. This might also include the deletion of existing words and the creation of new words if, in the latter case, the scientific definition and meaning has no linguistic equivalent in a given language. Let's take as an example the term traceability which by definition describes a way to achieve quality (accuracy, comparability) in chemical measurements. The equivalent in German would be Rückführbarkeit but in the respective DIN-norm the term Rückverfolgbarkeit is used, the linguistic meaning of which is "follow the way (track) back". Consequently, the term Rückverfolgbarkeit is part of providing assurance of quality and not of creating quality. Unfortunately, there is no English word for Rückverfolgbarkeit. There are two ways of solving this problem: one is to create a new English word and the other is to introduce the German word into the English language.

    We are willing to "grasp the nettle" and open the debate on this issue by proposing the term trackability to cover this concept.


    It is proposed that the EURACHEM Education and Training Working Group should be the catalyst which will promote a wider debate of the issues raised by this glossary of terms. All analytical scientists are urged to contribute to the debate and work towards a consensus on the usage of the key terms covered by the glossary.

    This debate can be carried forward by addressing your comments to:

    Prof Dr Helmut Günzler, Managing Editor, Accreditation and Quality Assurance, Bismarckstraße 4, D-69469 WEINHEIM, GERMANY, for consideration by the Education and Training Working Group.

    Alternatively, comments can be sent by Email only to:

    Dr John Fleming, Laboratory of the Government Chemist, Email:

    Dr John Fleming, LGC, UNITED KINGDOM
    Mr Heiner Albus, Philipps-Universität Marburg, GERMANY Prof Dr Bernd Neidhart, Philipps-Universität Marburg, GERMANY Prof Dr Wolfhard Wegscheider, University of Mining & Metallurgy, AUSTRIA

    Eurachem Reports

    IMEP6 Soon to be Evaluated

    The International Measurement Evaluation Programme (IMEP) has now completed its 6th measurement round, (IMEP6) Trace Elements in Water. An overview of results was recently presented at a EURACHEM/CITAC workshop1 which attracted considerable interest from the delegates. IMEP is coordinated from the Institute for Reference Materials and Measurements (IRMM), and is run under the auspices of IUPAC, EURACHEM, EUROMET and CITAC. The programme aims to be a tool for field laboratories to compare their results to SItraceable values and is also offered to regulating and accrediting bodies. Samples with undisclosed values are sent to interested laboratories. They return their measurement result with a statement of uncertainty, claiming to embrace the "true value". The SItraceable values are established by Isotope Dilution Mass Spectrometry (IDMS) which has the potential to be a primary method of measurement.2 For IMEP6, this was done in collaboration with NIST (USA) and University of Regensburg (Germany). Uncertainty ranges are evaluated according to ISOBIPM and EURACHEM guidelines.3,4 A strategy of IMEP is that the SItraceable values, which will serve as references, should be obtained by means of well understood measurement processes, rather than from averaging a number of values from different analytical techniques. IMEP rounds are run in cases where the objective evaluation of measurement results is important.

    In IMEP6, fourteen trace elements (Ag, B, Ba, Cd, Cu, Fe, Li, Mo, Ni, Pb, Rb, Sr, Tl and Zn) were under investigation in a synthetic and natural water material.5 Some 200 laboratories in 30 countries participated in this IMEP round. 29 participants were regionally coordinated from Chile. The first results from the certification work and evaluation of participants' results will appear in 19976,7.

    IMEP rounds planned in near future are shown in the table (bottom right). IMEP7, Trace elements in Human Serum, is being planned in close cooperation with organisers of external quality assurance programmes in the Nordic countries. There will, however, be room for approximately 150 international participants.

    Laboratories interested in this or in any other future round, or simply in more information, please contact:

    Mrs. Lutgart Van Nevel
    Tel: +32 (0)14 571 702, Fax: +32 (0) 584 273; 14 591 978

    Dr. Philip Taylor
    Tel: +32 (0)14 571 615, Fax: +32 (0)14 584 273; 591 978

    Dr Philip Taylor, Prof Dr Paul De Bièvre, Mrs Lutgart Van Nevel, Dr Ulf Örnemark
    IRMM, Belgium


    1. EURACHEM/CITAC, Workshop on Traceability and Comparability of AmountofSubstance Measurements, Leeuwenhorst Congres Centrum, Noordwijkerhout, The Netherlands, 46 September 1996.
    2. Comité Consultatif pour la Quantité de Matière (CCQM), 'Report of the l't Meeting', BIPM (Editor), Pavillon de Breteuil, F92312 Sevres Cedex, France, April 1995.
    3. 'Guide to the Expression of Uncertainty in Measurement', International Organisation for Standardisation ISO), ISBN9267101889, Geneva, Switzerland, 1993.
    4. 'Quantifying Uncertainty in Analytical Measurement', EURACHEM, ISBN 0948926082, 1995.
    5. 'The International Measurement Evaluation Programme (IMEP), IMEP6, Trace Elements in Water, Report to the Participants', Report GE/RSIM/25/1996, IRMM, September 1996.
    6. I. Papadakis, P. Taylor and P. De Bievre, 'SI-Traceable Values for Cadmium Concentrations in the Water Samples of IMEP6', accepted for publication in Fresenius J. Anal. Chem.
    7. U. Ornemark, P. Taylor and P. De Bievre, 'Certification of Rubidium in Water Material for the International Measurement Evaluation Programme (IMEP) using Isotope Dilution Inductively Coupled Plasma Mass Spectrometry', submitted for publication in J. Anal. At. Spectrom.
    8. A. Lamberty, L. Van Nevel, J.R. Moody and P. De Bievre, Accred. Qual. Assur., 1996, 1, 71.

    IMEP Rounds Planned in the Near Future

    Elements of Interest
    IMEP-7Trace Elements in Serum Ca, Cl, Fe, K, Li, Mg, Na, Se, Zn1997-98
    IMEP-8n(13C)/n(12C) in CO2
    IMEP-9Trace Elements in Water Same as in IMEP-6 and similar to IMEP-381997-98

    EURACHEM / EUROMET Interface Group

    EUROMET Amount of Substance Projects

    300 Intercomparison of Definitive
    Method for pH Measurement.
    Comparison Completed Mrs Petra

    DE, DK, HU, IT, PL
    313 Realising Comparability of Primary
    Gas Standard Mixtures. (PSM)
    Co-operationAgreed Mr Anton Alink NPL, NmiGB, NL
    316 Realising raceability by
    Tn(13C)/n(12C) Measurements in CO2 (IDMS)
    Co-operation Agreed Prof Dr G Dube IRMM, PTBCE, DE
    332 Determination of Trace Elements in WaterTraceability Agreed TBA (Contact Prof Dr Paul De Bièvre) IRMM, PTB CE, DE
    333 Determination of Iron in Milk Powder Traceability Agreed Dr P Taylor IRMM, LNE, PTB, VTT CE, DE, FI, FR
    366Documenting Water Purity by Electrolytic Conductivity Comparison Agreed Hans D Jensen DFM, Nmi, NPL, PTB, OMH, BNM, OFMET, NIST CH, DE, DK, FR, GB, HU, NL, US
    370Intercomparison of Primary Standard Measurement Devices for pH Comparison Agreed Mrs Petra Spitzer Merck, KGaA, PTB, Radiometer A/S, U. of Newcastle, OMH, U. of Milan, GUM DE, DK, GB, HU, IT, PL
    381Comparison of Electrolytic Conductivity measurements at 0.01, 0.1 and 1.0 S/m Comparison Agreed Hans D Jensen BNM, DFM, Nmi, NPL, OMH, PTB, SMU, VTTDE, DK, FI, FR, GB, HU, NL, SK

    Eurachem Reports

    The use of expiry dates for Chemicals & Reagents

    OECD GLP guidelines state that reagents should be labelled, as appropriate, indicating source, identity, concentration and stability information, the preparation date, earliest expiration date and specific storage instructions.

    EURACHEM's chemical laboratories guide says that reagents prepared in the laboratory should be labelled to identify substance, strength, solvent, any special precautions or hazards, restrictions of use and date of preparation and/or expiry. Similar guidance is given in the CITAC Guide.

    Altogether these documents, with EN 45001 and GLP, only recommend the use of expiry dates of a reagent on the label, without giving specific guidance.

    Not surprisingly, the most common problem a joint EUROLAB / EURACHEM-NL Working Group (WG) encountered was the GLP requirement to have an expiry date for every reagent used. The WG recommended: "The most practical solution is to develop a policy for arriving at sensible expiry dates for every chemical used. To avoid unnecessary retesting of expired chemicals, one should consider the chemical stability of the compound under storage conditions and the turnover time in relation to the amount purchased.". 1 This is a promising proposal, since each experienced analyst could lay down a sensible expiry date for the reagent in question.

    However, the WG still considers it necessary that even chemicals like NaCl should have an expiry date.

    To solve the problem, I propose the following:

    1. To avoid unnecessary measures and expenditures, the listing of an expiry date should not be mandatory.
    2. Depending on the purpose of the test and on the chemicalphysical nature of the reagent / chemical, the analyst should make this decision based on professional judgement.

    Dr Werner Steck

    Any comments on this article should be addressed to Dr Werner Steck or the EURACHEM Secretariat


    1. EUROLAB TCQA WG 2 and EURACHEM Netherlands WG 3; Final draft "Quality Assurance according to EN 45001 and OECD GLP A guide to simultaneous implementation 1996", Section 2.1.

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