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.     

Metrology in Iceland: a status report

 The metrology system in Iceland has been reviewed and developed in the light of the increased needs of industry and other users of the system, in some cases to comply with the requirements of the agreement between the European Union and the European Economic Area which the Icelandic government signed in 1992. After a short historical review, the current legislation is explained, the metrological infrastructure is described, and the plans for the coming years are discussed. Received: 27 November 1995 Accepted: 18 December 1995     

Chemical measurement and the law: metrology and quality issues

To facilitate just and sound decisions legal measurements must be reliable. The aim of this paper is to explore how this is currently achieved and how it might be better done. It considers the different types of legal proceedings, the role of chemical measurement, level of proof, the different types of chemical measurement, measurement units, the role of government, the chemical measurement industry and its control, legal metrology and the development of a measurement system based on metrological principles. It is argued that recent developments provide the basis for a robust support system, that but more needs to be done. It is also argued that the conventional approach to legal metrology has little place in chemical measurement, but that some controls are needed in some areas. In particular, a harmonised approach to international measurement standards is advocated. Received: 29 December 2000 Accepted: 8 January 2001     

The role of the Czech Metrology Institute in the field of metrology in chemistry

 The main role of a national metrological institute is to assure metrological traceability in the country. Metrology in chemistry is a developing field with specific features quite different from physical metrology and it is very difficult to establish a metrological system in chemistry based on the work of a single national institute, especially in small countries. For this reason the Czech Metrology Institute (CMI) has helped to establish the Association of National Reference Laboratories (METROCHEM) which is responsible for ensuring the traceability of chemical measurements in the Czech Republic. CMI is expected to carry out reference material certification (according to the Law on metrology) and develop special fields (electrochemistry, moisture and protein in grains).     

Assessing publically financed metrology expenditure against economic parameters

The objective of this paper is to provide an economic perspective to those involved in public financing of the national metrology infrastructure. Whereas justifications for subsidising the national metrological activities are often historically biased, we raise the importance of economic considerations, which could be used during prioritisation. The expenditure in measurement and metrology infrastructure of European countries are compared to economic indicators for quality of life. Various proxies are used, such as measuring instruments sale (for measurement infrastructure) and data from the BIPM’s KCDB (as a proxy for national standards). As the EU Internal Market also holds for the provision of metrological services, the paper exposes possible trends regarding public financing to the sector.

Metrology infrastructure for sustainable development of the Americas: the role of SIM

Reliable measurements are essential to guarantee all aspects required for the sustainable development of nations. There is an increasing awareness of the need to discuss, compare and improve infrastructures in the context of global economic efficiency, and market access for goods and services for both developed and developing countries. This is where metrology, standardization and conformity assessment come in. In order to further develop these activities, countries have been organizing themselves into regional cooperation groups. The Inter-American Metrology System (SIM) brings together the National Metrology Institutes of all 34 OAS member countries, aiming at the further development of a sound metrological basis, what lays in the basis of the technical infrastructure necessary for the sustainable development. In this paper the goals and objectives of SIM and some of its main projects will be analyzed, emphasizing the initiatives of chemical metrology and of quality management systems in the region.     

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.     

Optimising calibration and measurement capabilities in terms of economics in conformity assessment

Calibration measurement capabilities (CMC) are key factors in declaring the metrological performance of national metrology institutes (NMIs). Different countries have different CMC capabilities, reflecting both the existing measurement science competence as well as the perceived national needs for traceable calibration. This paper deals with increasing interest in decision-making in conformity assessment in terms of effective costs associated with measurement, testing and incorrect decision-making. The work examines the CMCs of calibration laboratories and NMIs with economic decision theory, in particular, in terms of customer satisfaction and with respect to conformity assessment issues. Optimal strategies for calibration costs, maintenance of national measurement standards, testing and production costs are illustrated in practical examples. CMCs are an essential instrument to enable conformity assessment both for product safety, legal metrology, quality requirements as well as scientific research. The newly defined term “target measurement uncertainty”, introduced in the latest international metrology vocabulary (VIM), should be therefore always related to appropriate CMCs and related dissemination paths in the whole conformity assessment procedure. These requirements are clear and transparent justification for the development of required national metrological infrastructures, in order to fulfil the requirements of target measurement uncertainty for intended use or application in the particular conformity assessment procedure.     

Informationsgewinn bei analytisch-chemischen Messungen

Summary The aim of every analytical experiment is to gain information about a particular chemical system. In order to design and carry out such an experiment it is necessary to take into consideration the chemical properties of the matter as well as the metrological rules inherent in the analytical method applied. In this aim (to obtain information) and in the manner of working (to regard chemical properties and metrological rules) analytical chemistry can be seen as being a uniform and independent scientific discipline. The different analytical methods and the numerous analytical problems can then be described in uniform manner. The different measuring parameters and steps in analytical work can all be reduced to uniform terms and processes. The treatment and evaluation of the signal produced in the analytical experiment is always at the centre of all discussions. The uniform theoretical interpretation of seemingly different methodological terms makes a standardized nomenclature possible. The aim of effectively obtained information explains the preference of certain analytical methods for trace analysis, structure analysis, multicomponent analysis or other analytical problems. Furthermore, it is possible to derive useful strategies for applying an analytical method or managing an analytical problem. Finally, tendencies can be shown for the development of analytical methods, which are particularly effective in obtaining information.     

Teaching metrology and quality in chemistry based on methods of mathematical statistics and e-learning

Chemistry students do not usually have the necessary background in mathematical statistics to study metrology and quality principles in chemistry. Even when the students have studied mathematical statistics, it is helpful to refresh their statistical knowledge, focusing on specific applications to metrology and quality in chemistry. Therefore, when planning a course for teaching metrology and quality it is important to achieve a harmonized interaction of metrological and quality issues with the supporting statistical issues. Additional possibilities for learning the relevant subjects originate from the Internet (e-learning). Such a lecture course developed and delivered during the five years since 2003 at the Hebrew University of Jerusalem is discussed in the paper.     

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).     

On practical metrology and chemical analysis: etalons and traceability systems

 National measurement systems are infrastructures to ensure, for each nation, a consistent and internationally recognised basis for measurement. Such complex systems have historical, technical, legal, organisational and institutional aspects to connect scientific metrology with practical measurements. Underlying any valid measurement is a chain of comparisons linking the measurement to an accepted standard. The ways the links are forged and the etalons (measurement standards) to which they connect are defining characteristics of all measurement systems. This is often referred to as traceability which aims at basing measurements in common measurement units – a key issue for the integration of quantitative chemical analysis with the evolving physical and engineering measurement systems. Adequate traceability and metrological control make possible new technical capabilities and new levels of quality assurance and confidence by users in the accuracy and integrity of quantitative analytical results. Traceability for chemical measurements is difficult to achieve and harder to demonstrate. The supply of appropriate etalons is critical to the development of metrology systems for chemical analysis. An approach is suggested that involves the development of networks of specialised reference laboratories able to make matrix-independent reference measurements on submitted samples, which may then be used as reference materials by an originating laboratory using its practical measurement procedures. Received: 31 July 1995 Accepted: 19 August 1995     

Some Latin American experiences concerning teaching of chemical metrology

In this paper, 15 years of the experiences acquired concerning the teaching of chemical metrology in Latin America are presented. These include postgraduate and undergraduate activities developed in eight countries. The combination of theoretic and practical activities and the sequence of learning from metrological, statistical, and chemometrical backgrounds up to practical activities in personal computers are basic and motivate the learning process. Care is taken to promote the metrological approach and thinking in analytical chemistry. The learning of computing techniques plays an important role, combining graphic and numerical techniques for data analysis. The role of examples during the teaching process is analyzed and recognized. The introduction of a general model of errors permits one to approach different topics on a metrological basis. The metrological approach of uncertainty based on the theory of errors permits one to develop the topic. Undergraduate students acquire a basic metrological knowledge and other experiences are also presented. Recommendations for undergraduate and postgraduate programs are pointed out.     

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     

Metrological traceability chain for PCBs: I.N.Ri.M. activity

Metrology in chemistry has its own features, which distinguish it from classical metrology: due to the lack of primary methods applicable in routine measurements, metrological traceability of measurement results can be achieved by using in a proper way suitable certified reference materials (CRMs), which can assure a direct relation to a reference. This article deals with the activity of the Italian National Institute of Metrological Research (Istituto Nazionale di Ricerca Metrologica—I.N.Ri.M.) on the analysis of various polychlorinated biphenyls congeners in organic solution by means of gas-chromatography coupled with mass spectrometry. The metrological traceability approach in the quantification step is pursued via calibration solutions prepared by gravimetrically diluting a CRM. The uncertainty for the calibration solutions was evaluated taking into account all the relevant contributions.     

面向共享的高分子材料网络数据库的设计和实现

以国家材料科学数据共享网为依托,我们建立了一个大型的高分子材料数据库并已向公众开放访问。数据库主要面向科研工作人员和工业企业等,提供基于高分子材料工业产品信息的数据共享服务。该数据库涵盖塑料、橡胶、纤维、涂料、胶粘剂、加工助剂等高分子领域主要的材料类型,目前已纳入7 000余个牌号的50 000多条数据。针对高分子材料类型的复杂性,该数据库采取了网状带冗余的分类方式以使一些组成复杂的材料可通过多种分类路径查询到。数据入库前,通过在数据生产、搜集、整合等多个过程中的评估以确保数据质量和可靠性。入库的数据也从数据来源、评估结果、修改记录等多个方面进行标记,以便后期进一步进行核对与评估。     

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)     

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.     

Exact analytic computer calculation on a four-center integral with slater orbitals

A method has been developed for reducing an initial sixfold four-center integral to a linear combination of a finite number of terms containing elementary and special functions. The maximum order of integration in the closed expressions is two. The method has been implemented with computers designed to automate handling literal expressions, and the necessary programs have been written. A four-center integral second in complexity has been calculated.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 4, pp. 491–494, July–August, 1986.