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Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement (v.5, #10-11)
The 3rd EURACHEM Workshop on Traceability, Bratislava, Slovak Republic, 6–8 September 1999
by Jan Garaj (pp. B407-B408).
The consequences of the mutual recognition of measurement standards for international metrology by Jean Kovalevsky (pp. 409-413).
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.
Keywords: Key words Metrology; Comparisons; Chemistry; Standards
What can we learn from traceability in physical measurements? by A. Williams (pp. 414-417).
An international system for providing traceability for the results from physical measurements has been under continuous development since the introduction of the Convention of the Metre over 100 years ago. Such a system has only been in existence for chemical measurements for about a decade and there is much that can be learnt from the way in which traceability has developed in physical measurements that will help its development for chemical measurements. First a number of myths that have grown up about the differences between these are examined. This is followed by a description of examples from physical measurements, which have important lessons for the ways in which traceability for the results of chemical measurements can be established.
Keywords: Key words Traceability; Physical measurements; Chemical measurements
How to achieve international comparability for chemical measurements by W. Richter (pp. 418-422).
It is the central aim of the current activities of metrology in chemistry to build confidence in the reliability of chemical measurement results so that they are accepted without costly duplication being necessary. An important prerequisite for such confidence is comparability based on traceability to recognised common references, ideally the SI units. Since metrology is organised within a national framework according to the national laws and regulations, a two-step procedure is to be followed to achieve international comparability for chemical measurements which is increasingly required as a result of the globalization of trade and economy: (1) establishment of national traceability structures for chemical measurements and (2) mutual recognition of the national traceability structures on the basis of equivalence criteria. The first step is at present being taken in many countries. Examples are presented for Germany. The second step has been initiated by the Mutual Recognition Arrangement (MRA) of the Meter Convention for national measurement standards and measurements and calibrations provided by national metrology institutes, which is based on international comparison measurements (key comparisons) carried out on the national standards level. Chemical analysis is included in this process through the Consultative Committee for Amount of Substance (CCQM).
Keywords: Key words Chemical measurements; Comparability based on traceability; Traceability structures; International equivalence
The key elements of traceability in chemical measurement: agreed or still under debate? by Paul De Bièvre (pp. 423-428).
Talking about "traceability" means talking about a "property of the result of a measurement", about "the value of a standard", about "stated references" and about an "unbroken chain of comparisons". It describes by which comparison, and to which other value, the result of a measurement has been obtained, i.e. is "traceable to". It is about the underlying structure of the measurement process of the result of a measurement and therefore about the authority of the result. Since values carried by (certified) reference materials have also been obtained by measurement, the definition of traceability equally applies. Traceability in the context of reference materials is also about the authority of the values carried by the (certified) reference materials and is, therefore, of key importance for the authority of the reference materials themselves. Hence, values of results of measurements constitute part of the traceability chain and their uncertainties are an intrinsic accompanying phenomenon. Uncertainties need a traceability chain against which they can be evaluated, and a traceability chain is an a priori requirement for evaluating the uncertainty budget of a measurement result. An attempt has been made to exemplify "traceability" chains in some types of chemical measurement and to identify the degree of international agreement on the key elements of "traceability". It is concluded that there is less than universal agreement on this issue. The debate should continue in order to arrive at the international understanding and agreement needed, as "traceability" is now being incorporated in the International Organization for Standardization (ISO), the International Laboratory Accreditation Co-operation (ILAC) and in other "guiding" or regulatory documents. It is also the reason why the Institute for Reference Materials and Measurements (IRMM) has taken up the study of the concept in its core programme on Metrology in Chemistry, and why it sponsored the Workshop in Bratislava.
Keywords: Key words Traceability chain; Metrology in chemistry; Reference material; Comparisons values of standards
The practical realization of the traceability of chemical measurements standards by Bernard King (pp. 429-436).
Metrology is based on the concept of traceability. Traceability provides a means of relating measurement results to common standards thereby helping to ensure that measurements made in different laboratories are comparable. Good progress has been made in the application of metrological principles to chemical measurement, but there remains confusion about how you actually achieve traceability in a practical way.This paper elaborates on the meaning and application of much used phrases such as 'the value of a standard', 'stated references', 'unbroken chain of comparisons', and 'stated uncertainties'. It also explains how traceability can be established in a practical way for different types of stated references, namely pure substance reference materials, matrix reference materials, and primary and reference methods. Finally, traceability chains for some typical examples of chemical measurement are described.
Link to the SI via primary direct methods by M. Máriássy; L. Vyskočil; A. Mathiasová (pp. 437-440).
The possible approaches to realising a link to the SI system and the status of primary direct methods in the traceability chain of chemical measurements are discussed. Some results obtained with the new coulometric standard system are presented.
Keywords: Key words Traceability; Coulometry; Uncertainty; Primary methods
The role of reference materials by Adolf Zschunke (pp. 441-445).
In this article the role of reference materials is confined to chemical measurements only. Recognized reference materials are one of the tools to obtain comparability of analytical results. Recognition demands confidence in the reference materials and in the reference material producers. A reference material producer is a technical competent body that is fully responsible for the certified or other property values of the reference material. The "analyte" has to be specified in relation to the selectivity of analytical procedure. The full range of reference materials can be presented as a three-dimensional space of the coordinates: analyte, matrix and application. If reference materials are used for calibration or correction of calibrations they establish the traceability of results of chemical measurements. The traceability is only valid within a stated range of uncertainty. Pure substances can represent the unit of amount of substance. A precondition is the microscale specification of the analyte and the accurate determination of the main component and/or the impurities.
Keywords: Key words Reference materials; Traceability; Chemical identification; Amount of substance
Second edition of the EURACHEM Guide Quantifying Uncertainty in Analytical Measurement
(pp. 446-449).
Traceability and its role in interlaboratory comparisons (proficiency testing programmes), modeled on trace element determination in biological materials by Lars Jorhem (pp. 449-450).
Traceability is not always evident in proficiency testing programs, although this is a requirement in ISO/IEC Guide 43-1. The assigned, or "true", value in most programs is not traceable to an independent entity. The test materials should generally be similar in nature to those routinely tested by participating laboratories. This is far from always the case and it is important to realize that if the difference is large, there may be no traceability to the testing program. It is also important that results from participation in proficiency tests are cited when papers are published, in order to enhance reliability/credibility of the published data.
Keywords: Key words Traceability; Proficiency testing; Elements
Quality assurance systems in research and routine analytical laboratories by M. Prosek; Aleka Golc-Wondra; Adi Krasnja (pp. 451-453).
In our article we explain the connections between the implementation of quality assurance (QA) in research and routine analytical laboratories. J. K. Taylor claims that QA in an analytical laboratory consists of two independent but closely related terms, quality control and quality assessment. If we construct the QA system according to his ideas, problems concerning quality can be solved with only one concept regardless of the type of analytical laboratory. Therefore there is no need to introduce new QA standards for research laboratories as suggested in some papers. In the routine laboratory quality control is more important, while in the research laboratory quality assessment is dominant.
Keywords: Key words Quality assurance; Quality control; Quality assessment; TQM; GLP