Conformity assessment and metrology: update on the state of affairs

A couple of years ago, ISO CASCO launched a major project of transforming all the existing ISO Guides on conformity assessment to a comprehensive series of ISO standards 17000 being now in various stages of development. As the concept of traceability underpinning all measurements has been a basic mission of metrology, a number of these standards have a direct bearing on metrology. The series is logically based on a definition standard, ISO 17000, giving, among others, a guidance which activities fall under conformity assessment. The fact that calibration does not, might have important consequences which must yet be assessed. A controversial discussion on some issues has been in progress concerning ISO 17011 on accreditation bodies which touches both on national metrology institutes (NMIs) with an accreditation function and on calibration labs at large. ISO 17040 on peer review could be used with an advantage to support mutual recognition arrangements among a limited number of bodies of a specialized expertise (e.g., CIPM MRA among NMIs under the Metre Convention). ISO 17025 has been the most important standard for the metrology community and has undergone a major overhaul taking on board the uncovered requirements from ISO 9001:2000. In general, the paper will give an update on the developments outlined above and discuss the consequences and further steps from the viewpoint of metrology.     

Metrological concept for comparable measurement results under the European water framework directive: demonstration of its applicability in elemental analysis

Within the scope of a project of the “European Association of National Metrology Institutes??(EURAMET), a European metrological dissemination system (network) providing traceable reference values assigned to matrix materials for validation purposes is described and put to the test. It enables testing laboratories (TL) to obtain comparable results for measurements under the “EU Water Framework Directive 2000/60/EC??(WFD) and thus, to comply with a core requirement of this very directive. The dissemination system is characterized by the fact that it is available to all laboratories throughout Europe which intend to perform measurements in the context of the WFD and that it can ensure sustainable metrological traceability to the International System of Units (SI) as a reference point for the measurement results. This dissemination system is set up in a hierarchical manner and links up the level of the national metrology institutes (NMI) with that of the TLs via an intermediate level of calibration laboratories (CL) by comparison measurements. The CLs are expert laboratories with respect to the measurement of the analytes considered here (within the project, the CLs are called potential calibration laboratories (PCL)) and are additionally involved in the organization of comparison measurements within the scope of regional quality assurance (QA) systems. Three comparison measurements have been performed to support the approach. A total of about 130 laboratories participated in this exercise with the focus on the measurement of the priority substances Pb, Cd, Hg, and Ni defined in the WFD. The elemental concentrations in the water samples roughly corresponded to one of the established environmental quality standards (EQS), the annual average concentration (AA-EQS), which is defined in the daughter Directive 2008/105/EC of the WFD. It turned out that a significant number of TLs still need to improve their measurement methods in order to be able to fulfill the minimum requirements of the WFD, in particular, with regard to the elements Cd and Hg probably due to their low EQS values. Furthermore, it became obvious that the hierarchical dissemination system suggested here actually corresponds to the measuring capabilities of the three participating groups (NMIs, PCLs, and TLs).     

On the specific experience of national metrology institutes (NMIs) with national accreditation bodies (NABs)

The following paper addresses the experience of certain national metrology institutes (NMIs) with national accreditation bodies (NABs), in particular in small countries with emerging economies in new EU or candidate member states. Specific cases have been analysed primarily in some Central and South-East European countries. NABs under consideration are, in principle, members of European Co-operation for Accreditation (EA). EA cross-frontier policy in these cases will be discussed and resulting dilemmas outlined. Focus will be given to the problems of NMIs also performing calibrations, commercial calibration laboratories, and their relations with NABs. Due to numerous problems of smaller NABs, cross-frontier policy should stimulate cooperation between foreign and local accreditation bodies not only at the request of the calibration laboratory or some other conformity assessment body, but at the request of the local accreditation body in order to provide the best service for their local economy. As a solution to the accreditation problems, this paper proposes a process of gradual formation of a common European pool of experts, real-life common practices and, finally, maybe even some form of joint European accreditation service. The opinions expressed in the paper are personal statements of the author, and do not necessarily reflect the official opinions of the institutions of the author. Papers published in this section do not necessarily reflect the opinion of the Editors, the Editorial Board and the Publisher.     

Evaluation of the state-of-the-art measurement capabilities for selected PBDEs and decaBB in plastic by the international intercomparison CCQM-P114

An international intercomparison involving eight national metrology institutes (NMIs) was conducted to establish their current measurement capabilities for determining five selected congeners from the brominated flame retardant classes polybrominated diphenyl ethers and polybrominated biphenyls. A candidate reference material consisting of polypropylene fortified with technical mixtures of penta-, octa- and decabromo diphenyl ether and decabromo biphenyl, which was thoroughly assessed for material homogeneity and stability, was used as study material. The analytical procedures applied by the participants differed with regard to sample pre-treatment, extraction, clean-up, employed calibrants and type of calibration procedure as well as regarding analytical methods used for separation, identification and quantification of the flame retardant congeners (gas chromatography coupled to an electron capture detector (GC-ECD), gas chromatography-mass spectrometry in the electron ionisation mode (GC-EI-MS), gas chromatography-mass spectrometry in the electron capture negative ionisation mode (GC-ECNI-MS), and liquid chromatography-inductive coupled plasma-mass spectrometry (LC-ICP-MS)). The laboratory means agreed well with relative standard deviations of the mean of means of 1.9%, 4.8%, 5.5% and 5.4% for brominated diphenyl ether (BDE) 47, 183 and 209 and for the brominated biphenyl (BB) congener 209, respectively. For BDE 206, a relative standard deviation of 28.5% was obtained. For all five congeners, within-laboratory relative standard deviations of six measurements obtained under intermediate precision conditions were between 1% and 10%, and reported expanded measurements uncertainties typically ranged from 4% to 10% (8% to 14% for BDE 206). Furthermore, the results are in good agreement with those obtained in the characterization exercise for determining certified values for the flame retardant congeners in the same material. The results demonstrate the state-of-the-art measurement capabilities of NMIs for quantifying representative BDE congeners and BB 209 in a polymer. The outcome of this intercomparison (pilot study) in conjunction with possible improvements for employing exclusively calibrants with thoroughly assessed purity suggests that a key comparison aiming at underpinning calibration and measurement capability (CMC) claims of NMIs can be conducted.

One way of disseminating reference values with demonstrated traceability and demonstrated uncertainty to field laboratories: IMEP

An operational interlaboratory comparison programme is described which disseminates SI-traceable reference values to laboratories worldwide. These reference values have an uncertainty and traceability that is demonstrated at the highest metrological level. Participating laboratories can use these values to establish the degree of equivalence of their measurement results and can use this to support their measurement capability claims, e.g. towards third parties. The programme has been run by the Institute for Reference Materials and Measurements (IRMM) since 1988, in the first phase as an awareness programme. Currently, IRMM is focusing its efforts on educational aspects of metrology via a collaboration with the European Co-operation for Accreditation, national metrological institutes (NMIs) and interested academic networks. The viewgraphs used are presented in the “Electronic Supplementary Material” of this ACQUAL issue.     

CCQM primary methods symposium: how far does the light shine?

The Consultative Committee for Amount of Substance (CCQM) has the task of organizing a comprehensive set of international comparisons to establish the technical basis for the mutual recognition of measurement capabilities among the national measurement institutes (NMIs) in the field of chemical measurement. The challenge that the CCQM faces is to identify, design, and conduct a limited number of key comparisons to enable the assessment of measurement comparability among NMIs across the entirety of ’chemical measurement space’. This is no easy task because the field of chemical metrology is extremely diverse and multidimensional, owing to the number of measurand types, concentrations, and matrix types of importance. The ”CCQM primary methods symposium: how far does the light shine?” was organized to provide information and initiate discussions to assist in this challenge, and clarify how the concept of a primary method of measurement could be instrumental in achieving this goal.     

An international assessment of the metrological equivalence of higher-order measurement services for creatinine in serum

The Consultative committee for amount of substance-metrology in chemistry (CCQM)-K80 Key Comparison directly assessed the equivalence of many of the world’s higher-order value-assigned materials (HOVAMs) for creatinine in human serum. This 2009 international study compared the certified values and uncertainties of the materials using measurements made under repeatability conditions. The study evaluated 17 materials submitted by 6 national metrology institutes (NMIs). The creatinine quantity in these materials ranged from 3 mg/kg to 57 mg/kg (about 0.3 mg/dL to 6 mg/dL or 30 nmol/L to 500 nmol/L). All materials were stored and prepared according the specifications provided by the participating NMIs. Samples were processed and analyzed under repeatability conditions by one analyst using isotope-dilution liquid chromatography–mass spectrometry in two measurement campaigns. The certified values and repeatability measurements were compared using uncertainty-weighted generalized distance regression. The instrumental repeatability relative standard deviation was 1.2%. The measurement design required assessment of within-unit and between-campaign variability in addition to measurement repeatability. At a 95% level of confidence, the certified values for all 17 materials agreed to within their assigned uncertainties. CCQM-K80 demonstrated the metrological equivalence of the currently available HOVAMs for creatinine in human serum and of the creatinine measurement services provided by the participating NMIs.     

Interlaboratory comparison for the determination of pesticide residues in Chinese cabbage

The results of and findings from an interlaboratory comparison among laboratories carrying out food testing of pesticide residues in the APEC (Asia–Pacific Economic Cooperation) region are presented and discussed to show critical roles of chemical metrology infrastructure in establishing traceability of measurements and in supporting existing measurement capability in safety and quality of food trade. The study material, which was prepared and certified by Korea Research Institute of Standards and Science (KRISS), was freeze-dried Chinese cabbage powder fortified with two organophosphorous pesticides (diazinon and chlorpyrifos). Among 14 participants, 12 laboratories were accredited based on ISO/IEC17025 and one laboratory was under assessment for the accreditation at the time of this study. Though all participants demonstrated very good intra-day repeatability and inter-day intermediate precision, many of them showed a large bias from the certified values. It is suggested that in addition to the accreditation system, economies are encouraged to develop appropriate chemical metrology infrastructure, which could effectively support laboratories to assure measurement traceability to SI, for which NMIs could play significant roles through their metrological services recognized in Mutual Recognition Arrangement (MRA) of the International Committee for Weights and Measures (Comité International des Poids et Mesures, CIPM).     

Exhaust gas analysers and optimised sampling, uncertainties and costs

Decision-making in the conformity assessment of exhaust gas analysers with due account of measurement uncertainty and limited sampling is considered. Risks of incorrect decisions where test results lie in the vicinity of a specification limit are assessed in terms of percentage probability and the costs of measurement and environmental consequences, with examples based on the metrological requirements on these analysers stipulated in the new EU Measurement Instrument Directive. An optimised uncertainty methodology is proposed for the first time in legal metrology based on quantitative testing of new instruments for type approval and initial verification, and gives valuable insight into traditional rules limiting uncertainty in conformity assessment in general. Further, an analysis of subsequent verification of exhaust gas analysers in use in society, leads to a new optimised uncertainty methodology based on attribute sampling.

A national traceability system for chemical measurements

Current developments in Germany for establishing a traceability system for chemical measurements are reported. The focus is on a dissemination mechanism which employs chemical calibration laboratories accredited within the framework of the German Calibration Service (DKD) and acting as "multipliers" between the national standards level and the user level by providing the user with calibration means which are traceable to the SI via national standards. At the national standards level, a network of high-level chemistry institutes coordinated by the national metrology institute, PTB, provides the primary references for chemical measurements.The use of the metrological dissemination system provided by the DKD also for chemical measurements is a logical extension of a traceability mechanism, successful for more than two decades in general metrology, to metrology in chemistry. In detail, traceability structures in clinical chemistry, electrochemistry, elemental analysis and gas analysis are described. This system has become an important part of the efforts made in Germany to support chemical laboratories in meeting the traceability requirements of the market and of legal regulations.     

The consequences of the mutual recognition of measurement standards for international metrology

After stressing the importance in the modern world of accurate and reproducible measurements, the actions taken by the Bureau International des Poids et Mesures to set up, together with the regional metrology organizations, a series of key comparisons are described. They are the technical foundation of a mutual recognition of national measurement standards arrangement prepared in conjunction with the National Metrology Institutes (NMIs). This arrangement also includes the recognition of calibration and measurement certificates issued by these institutes. Then, the consequences of this arrangement for trade are described. The case of chemical analysis is illustrated by the application of the Kyoto protocol on the reduction of greenhouse gases. But the global workload to be taken up by the International Committee of Weights and Measures, its Consultative Committee for Amount of Substance and the NMIs is huge.     

The use of certified reference materials in the Romanian traceability scheme

 For ensuring the traceability and uniformity of measurement results, the main objectives of national metrology programmes in chemistry are to calibrate and verify measuring instruments, to evaluate the uncertainty of measurement results and to intercompare the analytical results, etc. The concept of traceability has developed recently in chemical measurements, thus, an attempt to implement the principles of metrological traceability especially by appropriateness calibration using composition certified reference materials (CRMs) is underlined. Interlaboratory comparisons are also a useful response to the need for comparable results. The paper presents some aspects and practices in the field of spectrometric measurement regarding the metrological quality of the traceability by calibrating the instruments using suitable and reliable CRMs. The uncertainty of results, as a measure of the reliability that can be placed on them, has been adequately described in different documents and, as a consequence, some examples of evaluating the measurement uncertainty are described. The relationship between uncertainty and traceability, as two fundamental concepts of metrology which are intimately linked, is underlined. Received: 12 November 1999 / Accepted: 10 December 1999     

The consequences of the mutual recognition of measurement standards for international metrology

 After stressing the importance in the modern world of accurate and reproducible measurements, the actions taken by the Bureau International des Poids et Mesures to set up, together with the regional metrology organizations, a series of key comparisons are described. They are the technical foundation of a mutual recognition of national measurement standards arrangement prepared in conjunction with the National Metrology Institutes (NMIs). This arrangement also includes the recognition of calibration and measurement certificates issued by these institutes. Then, the consequences of this arrangement for trade are described. The case of chemical analysis is illustrated by the application of the Kyoto protocol on the reduction of greenhouse gases. But the global workload to be taken up by the International Committee of Weights and Measures, its Consultative Committee for Amount of Substance and the NMIs is huge.

     

Primary methods for the measurement of electrolytic conductivity

This paper surveys the state of the art for primary methods for the evaluation of electrolytic conductivity in aqueous solutions as they are currently carried out in several national metrological institutes (NMIs). The theoretical and practical basic knowledge of this measurement is described. Analysis of and comments on the different approaches are offered to give emphasis to technical difficulties and possible solutions. Further development is foreseeable, ensuring a common effort for the sharing of expertise that has been undertaken at the NMIs. In particular, improvements are expected towards traceable measurements of solutions with conductivity values lower than those actually standardized, down to the level of ultrapure water.     

Metrological traceability is not always a straight line

The two most important concepts in metrology are certainly “traceability to standards” and “measurement uncertainty evaluation”. So far the questions related to these concepts have been reasonably solved in the metrology of “classical quantities”, but for the introduction of metrological concepts in new fields, such as chemistry and biology, a lot of problems remain and must be solved in order to support international arrangements. In this presentation, the authors want to develop the strategy implemented at Laboratoire national de métrologie et d’essais (LNE) in metrology in chemistry and biology. The strategy is based on: (1) pure solutions for calibration of analytical instruments, (2) use of certified reference materials (matrix reference materials), and (3) participation to proficiency testing schemes. Examples will be presented in organic and inorganic chemistry. For laboratory medicine, proficiency testing providers play an important role in the organization of External Quality Assessment Schemes. For the time being, the reference value or the assigned value of the comparison is calculated with the results obtained by the participants. This assigned value is not often traceable to SI units. One of the methods suggested by LNE is to ensure the metrological traceability to SI units of the assigned value for the more critical quantities carried on analytes by implementing the Joint committee for traceability in laboratory medicine reference methods.     

Regional cooperation in proficiency testing: strategy planning and practical experiences in Western Balkan countries

The article describes the project of regional cooperation in proficiency testing within CARDS 2006 (assistance programme to the Western Balkans), which was coordinated by European Committee for Standardization, European Commission and European Free Trade Association and conducted by the University of Ljubljana, Faculty of Electrical Engineering, Laboratory of Metrology and Quality. The later is the holder of the national standard for thermodynamic temperature as well as an accredited proficiency testing provider and also accredited as a calibration, testing and inspection laboratory. It is also responsible for graduate study programme Quality Engineering. Proficiency testing was considered as a core activity of the entire project, but additionally as a very appropriate platform for knowledge transfer of EU technical legislation in selected sectors, metrology, testing and quality assurance in general. The project had a high added value for participating laboratories in countries of Western Balkans, because it required an active role of all participating laboratories, assured participation of staff from national metrology institutions, all national accreditation bodies, and was supported by national quality infrastructures, such as standardization, governmental institutions etc. in the entire Western Balkans region. The activities stimulated progress in the area of conformity assessment, added knowledge to the implementation of technical directives and development of the technical part of national legislation and therefore facilitated the process toward the accession to the European Union. The main objective was therefore to organize proficiency testing in those sectors (construction, consumer protection and environment) that were vital in the pre-accession process of countries seeking full implementation of EU technical legislation.     

Tunisian traceability system

The concept of metrology first appeared in Tunisia towards 1909. At the end of the 1990s, bodies for evaluating conformity of measurement at different levels have been instituted to meet calibration and testing needs of the national industry. These bodies were divided into three categories: Class A where we find mainly the Central Laboratory for Analysis and Testing LCAE and the National Defence Laboratory DEFNAT; these two laboratories are in charge of the technological upgrading of the other bodies of Class B which, in turn, would transfer their knowledge to the industries, the latter constituting Class C. Nowadays, the accreditation of Tunisian laboratories at the international level by recognized reference foreign bodies and participation in the European proficiency network enabled the national laboratories of Tunisia to establish the degree of equivalence between their measurement results and those of other foreign laboratories.     

A strategy for a national metrology institute to create a cost effective distributed metrology infrastructure for chemical measurements

A sound strategy for a national metrology institute (NMI) is proposed, describing how to set up an metrology infrastructure for chemical measurements. A national measurement infrastructure is defined as a collection of various measurement services (testing, calibration and reference laboratories) and the communication between these services. For clarity, in this paper the distributed metrology infrastructure covers those organisations that are involved in disseminating measurement traceability (i.e. the national metrology institute and the reference laboratories acting as national reference standard holders).The strategy aims at a proper support of sectoral field laboratories. It is based on a distributed metrology system. Such a system is composed of clearly identified national reference standard holders for particular measurement services (e.g. for a particular analyte in a particular matrix) co-ordinated via an NMI. Such national reference standard holders, appointed by the NMI, represent the best measurement capability inside the country, and their appointment is based on demonstrated measurement competence. They receive support (e.g. under contract) from the NMI to fulfil this role. They have the obligation to demonstrate their measurement capabilities on a regular basis and in a publicly open and transparent way.In particular and carefully selected cases, the NMI itself can and should act as national reference standard holder. The NMI should particularly devote a large part of its resources to cross-sectoral knowledge transfer, to advice and co-ordination. This can be achieved by participating in teaching/training, by supporting the accreditation, by being involved in advising governmental bodies in authorisation of laboratories and by assisting in the implementation of legislation.As a consequence, only when values produced at the NMI (or one of its designated national reference standard holders) are disseminated to field laboratories (e.g. for CRMs or as a calibration service) will it be necessary to have the NMI measurement capability recognised under the CIPM-MRA system.Such a distributed system requires an efficient communication tool between the three stakeholders concerned: the NMI, the national reference standard holder and the end users. The latter not only include the field laboratories, but also governmental bodies and the national accreditation body.Presented at the XVIIIth IMEKO Congress in Dubrovnik-Cavtat, June 22–27, 2003Further contributors to this paper: M. Buzoianu (National Institute of Metrology, Bucharest), W.Kozlowski (Central Office of Measures, Warsaw), P. Klenovsky, Frantisek Jelinek (CMI, Prague), C. Michael (State General Laboratory, Nicosia), Zsofia Nagyné Szilágyi, (National Office of Measures, Budapest), V. Patoprsty (Slovak Institute of Metrology, Bratislava), A. Todorova (SAMTS Sofia)     

Developments in accreditation of flexible scopes in Europe

Accreditation of testing and calibration laboratories is the most frequently used type of accreditation. European Co-operation for Accreditation (EA) as the European network of recognised national accreditation bodies covers accreditation of all types of conformity assessment bodies. In Europe, the number of accredited testing and calibration laboratories covered under the EA Multilateral Agreement is about 15,000 nowadays.     

Volume calibration of 1000 μl micropipettes. Inter-laboratory comparison

A EUROMET comparison “volume calibration of 1000 μl micropipettes”, between six national metrology institutes (NMIs), was performed during 2006 with the purpose of comparing results and uncertainty calculations. The objective of this paper is to describe the volume measure instruments, the model, the method, and to discuss the results and its associated uncertainties presented by each participating NMI.