Simple principles for metrology in chemistry: identifying and counting

We examine the problem of quantitative chemical measurement for well-identified substances, discuss the quantity called ‘amount of substance’, the means of expressing it, and its physical SI unit the mole. The everyday quantity which is a number of entities may be measured by the performance of two operations (identification and counting), the results of which may be communicated with two items of information (their name and the number of entities). We distinguish nominal, ordinal, interval and ratio scales of measurement and apply these to counting, referring to ordinal and cardinal numbers and Helmholtz’ analysis of measurement. Counting may be by direct serial numeration, direct parallel numeration, or comparative numeration. We discuss the limitations of serial numeration, the possibilities of parallel numeration, and the advantages of comparative numeration where a unit for counting in multiples (such as the analyst’s mole) may be used to define a scale on which equal numbers of objects correspond to equal values of some other physical quantity. We conclude that the numeration of very large numbers of objects is readily achieved but with unavoidable uncertainty, using operations which compare numbers of entities either to numbers of other entities or to some other quantity which accurately models numbers of entities.     

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)     

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.     

A participatory improvement activity of the EC-JRC to improve metrology in chemistry in EU candidate countries

In 2000, the European Commission-Joint Research Centre, Institute for Reference Materials and Measurements (EC-JRC-IRMM) set up a project to improve the scientific basis for metrology in chemistry (MiC) in EU candidate countries. Several activities were initiated (training, fellowships, sponsoring seminars, conferences and participation in the International Measurement Evaluation Programme – IMEP). A particular initiative, discussed here, was to assist each of the national measurement institutes of these countries to write a status report on MiC. Most importantly, the report was intended to be the end-product of a process to document the current status of MiC. Intentionally, this process involved not only the providers of services in MiC but all the major stakeholders in this activity (e.g. major field laboratories, accreditation bodies, regulatory bodies, educators, professional bodies). The status reports are intended to be the first step of the future improvement process. In those countries where writing of the status reports has been started (Slovenia, Poland, Bulgaria and Estonia) the first signs are that this process leads to better co-operation and particularly a better understanding of what the future role and activities of each of these stakeholders should be. Correspondence to N. Majcen     

The role of metrology in chemistry in the upholding of public health and food safety in Hong Kong

The Government Laboratory has been involved in the provision of analytical and advisory services since its formal establishment in 1913 in support of the needs of the community and the commitments of the Government of Hong Kong Special Administrative Region, China. One of the earliest areas of work involves the testing of food samples for maintenance of public health and food safety. Remarkable advances in technology in recent years coupled with the introduction of new policies and regulations, the launching of new international standards and requirements have all contributed to significant and ever-rising demand of accurate, specific, comparable and traceable measurements using the latest technologies for a wide variety of additives, contaminants, residues and genetically modified ingredients in food.Metrology, the science of measurement, has always played a key role in the development and validation of analytical methodologies in the Government Laboratory for the realization of its measurements to the highest level of accuracies and traceability to internationally recognized standards. Besides the application of the latest analytical technologies such as isotope dilution mass spectrometry, tandem mass spectrometry, real-time polymerase chain reactions, etc., the Analytical and Advisory Services Division of the Laboratory develops a quality assurance system in full compliance with the requirements of ISO/IEC 17025 and endeavours to ensure that every analytical methods are validated with the best applicable means and are fit for the intended purposes. In this presentation, the role and application of metrology in chemistry in the measurements pertaining to public health and food safety work undertaken by the Government Laboratory are discussed.Presented at International Symposium on Metrology in Chemistry, 2004 Beijing, China.     

Green analytical chemistry as an integral part of sustainable education development

1. Download : Download high-res image (137KB)
2. Download : Download full-size image

     

IMEP in support of the comparability of measurement results across the Romanian chemical metrology infrastructure

On the basis of quantitative chemical measurements many important decisions are made in support of legislation or in industrial processes or social aspects. For this reason it is important to improve the quality of chemical measurement results and thus make them comparable and acceptable everywhere. The measurement quality is important to enable an equivalent implementation of the European Union regulations and directives across an enlarged EU. In this context, the European Commission–Joint Research Centre–Institute for Reference Materials and Measurement (EC-JRC-IRMM) set up a programme to improve the scientific basis for metrology in chemistry (MiC) in EU candidate countries in the framework of EU enlargement. Several activities were initiated, such as training, fellowships, sponsoring of seminars, conferences and participation in interlaboratory comparisons. To disseminate measurement traceability, IRMM provides through its International Measurement Evaluation Programme (IMEP) an interlaboratory tool to enable the benchmarking of laboratory performance. IMEP emphasizes the metrological aspects of measurement results, such as traceability and measurement uncertainty. In this way it has become a publicly available European tool for MiC. The Romanian Bureau of Legal Metrology – National Institute of Metrology (BRML-INM) actively supports the participation of Romanian authorized and field laboratories in IMEP interlaboratory comparisons. This paper describes the interest of Romanian laboratories participating in this programme, the analytical and metrological problems that became relevant during these exercises and some actions for improvement. The results from Romanian laboratories participating in IMEP-12 (water), IMEP-16 (wine), IMEP-17 (human serum) and IMEP-20 (tuna fish) are presented. To conclude, the educational and training activities at national level organized jointly by the Romanian National Institute of Metrology (INM) and IRMM are also mentioned.     

Reliability of analytical information in the XXIst century

One of the most relevant bottlenecks of the progress of analytical sciences is the existence of adequate references in general and, in particular, of measurement standards for analytical processes and their proper use in the context of metrology in chemistry. Keywords such as traceability, uncertainty, calibration, etc. are crucial to characterise the analytical information. All of them can be summarised by using reliability as an overall analytical attribute. The main aim of this paper is the systematic consideration of this basic approach among the trends in Analytical Chemistry, particularly in qualitative analysis.     

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     

Chemical metrology, chemistry and the uncertainty of chemical measurements

Chemical results normally involve traceability to two reference points, the specific chemical entity and the quantity of this entity. Results must also be traceable back to the original sample. As a consequence, any useful estimation of uncertainty in results must include components arising from any lack of specificity of the method, the variation between repeats of the measurement and the relationship of the result to the original sample. Chemical metrology does not yet incorporate uncertainty arising from any lack of specificity from the method selected or the traceability of the result to the original sample. These sources of uncertainty may however have much more impact on the reliability of the result than will any uncertainty associated with the repeatability of the measurement. Uncertainty associated with sampling may amount to 50–1000% of the reported result. Chemical metrology must be expanded to include estimations of uncertainty associated with lack of specificity and sampling. Received: 29 May 2001 Accepted: 17 December 2001     

Uncertainty – The key topic of metrology in chemistry

 At the Second EURACHEM Workshop on Measurement Uncertainty in Chemical Analysis the author had the pleasure of chairing a working group on chemical metrology. This note presents some propositions arising from the preparation of, as well as from the discussion at and after, the working group session. Received: 29 October 1997 · Accepted: 26 November 1997     

Incorporating nuclear chemistry as an education tool in the undergraduate chemistry curriculum: A description of the curriculum project

Although many areas of major national need depend critically on professionals trained in nuclear and radiochemistry, educational opportunities and student interest in this area have declined steadily for the last twenty years. One major contributing factor to the lack of student interest is that most students in science and chemistry courses are never introduced to these topics. This deficiency in science curricula, coupled with the negative public perception towards all things “nuclear”, has resulted in a serious shortage of individuals with a background in this area. We propose to address this problem by “educating the educators” — providing faculty from two- and four-year colleges and high school science teachers with the curriculum materials, training, and motivation to incorporate these topics on a continuing basis in their curricula. Two advantages of this approach are: (1) it will generate scientists with a basic understanding of this field and (2) as teachers incorporate nuclear topics, many students will have the opportunity to reflect on the role of science in a technological society.     

Research on analytical chemistry in Brazil: an overview

An overview is presented of the beginnings, evolution and current status of research on analytical chemistry in Brazil. Among the various fields of chemistry two decades ago, Analytical Chemistry was considered one of the least developed in Brazil. In the last 15 years, however, research and development in this field have expanded considerably and today it is one of the most highly developed fields of Chemistry in Brazil. This paper offers a general overview of this evolution and some suggestions for possible routes for the future of analytical chemistry in Brazil.     

Metrology in chemistry: Part I. Current activities in Europe

 The paper (Parts I and II) reports the results of a survey carried out to assess the current situation in the field of metrology in chemistry within Europe and to identify future needs for work at the European level. Responses to a questionnaire covering 17 economic sectors and distributed to 17 countries plus the European Commission Joint Research Centre (EC JRC), together with input from a project group, EURACHEM and EUROMET provided the basis of the study. The questionnaire responses clearly indicated that only a minority of countries had clearly defined responsibilities for policy, funding and technical leadership. Similarly only a small number of countries was able to provide any information about levels of funding. Nonetheless, a variety of work is in progress and in some countries the effort is considerable. In other countries discussion is in progress and /or work is beginning. Part I covers the protocol for the study and reports current activities. Part II reports suggestions for future work, a strategy for metrology in chemistry and recommendations for the EC Fifth Framework Programme. Received: 11 January 1999 / Accepted: 4 January 2000     

Metrology in chemistry: Part II. Future requirements in Europe

 The paper (Parts I and II) reports the results of a survey carried out to assess the current situation in the field of metrology in chemistry within Europe and to identify future needs for work at the European level. Responses to a questionnaire covering 17 economic sectors and distributed to 17 countries plus the European Commission Joint Research Centre (EC JRC), together with input from a project group, EURACHEM and EUROMET, provided the basis of the study. Part I covers the protocol for the study and reports current activities. Part II reports suggestions for future work, a strategy for metrology in chemistry and recommendations for the EC Fifth Framework Programme.     

Proficiency evaluation as a traceability link in chemical metrology

Traceability implies comparison of the results of measurements, or comparison to national or international measurement standards. One of several approaches that have been used in chemistry to provide for such comparisons is distribution of proficiency evaluation materials which have been measured by a reference laboratory. A newer approach is based on receipt and measurement at a reference laboratory of materials that have been produced and analyzed by other laboratories. Traceability concepts and approaches to realization will be described together with discussion of the relative merits of various approaches. Extension into metrological fields other than chemistry will also be explored. Received: 14 November 2000 Accepted: 11 December 2000     

Uncertainty in photometric analysis: a case study

A procedure for estimation of measurement uncertainty of photometric analysis based on the ISO GUM method is presented. Two variations of the procedure—for the calibration graph and the standard addition method, respectively—are discussed. The variations are based on mathematical models involving 64 and 80 input quantities, respectively. The uncertainty of the result strongly depends on changes in experimental details. These dependencies are explored for a practical example of determination of the iron content of aluminum. The importance of taking uncertainty from sample preparation into account in uncertainty estimation is stressed. The number of effective degrees of freedom is calculated and discussed. The examples are available as GUM Workbench files in the Electronic Supplementary Material.Electronic Supplementary Material  Supplementary material is available for this article at .