Uncertainty of measurement. Twenty years afterwards

The application of the concept “uncertainty” causes considerable difficulties. In this paper an analysis of the intrinsic contradictions of the concept itself and its relationship with the statements of metrology is given with the aim of establishing possible reasons for these difficulties. As a result of this analysis several examples are presented to demonstrate the conflicts of the concept and its several statements in the general fundamental notions of metrology. Received: 16 February 2001 / Revised: 2 April 2001 / Accepted: 9 April 2001     

Error and Uncertainty in the Results of Chemical Analysis

Twenty years have elapsed since the concept of uncertainty was elaborated, which provided the basis not only for the INC-1 Recommendations but for some other international documents as well. However, the use of this concept presents considerable difficulties in some cases. In the submitted paper, starting from the basic metrological postulates, we have analyzed the concept and compared it with the concept based on the notion of the measurement error in order to reveal possible reasons for the above-mentioned difficulties. The analysis demonstrates the inconsequence of the concept of the uncertainty of measurement and contradictions between some of its postulates and the basic postulates of metrology. The cryometric determination of the degree of purity of benzoic acid and acetanilide were taken as examples to demonstrate the numerical equality between the estimated uncertainty and the error on the one hand. On the other hand, it was also shown that a distinction should be made between the uncertainty of the result of measurements and the uncertainty of the measurand. Drawbacks of the uncertainty concept were outlined, and it was shown that the elimination of these drawbacks would favor the application of the concept in particular cases.     

Metrology in Africa: role of the CAFMET

This article presents the CAFMET (African Committee of Metrology), a non-profit organization that aims to meet the needs of African countries in the field of metrology. Its objectives are to spread a metrology culture in Africa via various domains in metrology such as, analysis, tests, and calibration. The difficulties of the development of metrology in Africa and the different activities, events and projects of the CAFMET are all presented.     

组合回归分析法——盐酸标准滴定溶液浓度的标定

介绍和讨论了计量学中组合测量的概念和方法.在最小二乘法原理的基础上,结合化学计量学方法和化学滴定分析计量测试的特点,并参照 GB/T601-2002 标准,设计出盐酸标准滴定溶液浓度的组合回归标定方法,其内容包括:工作基准试剂 Na2CO3 的组合称量操作程序及其数据处理;试样溶液的组合滴定操作程序及其数据处理;常规测...     

Melting properties of molten salts and ionic liquids. Chemical homology,correlation, and prediction

The application of the concept of chemical homology to describe melting properties of molten salts and ionic liquids (ILs) is analyzed. This concept was used several years ago to correlate and predict properties of solids and more recently to correlate melting temperatures of ILs. To analyze the characteristics of the extended method, this is first applied to melting properties of organic substances for which abundant data are available. The method is extended to analyze its applicability for properties of molten salts and ILs such as glass transition temperature, heat of melting, and entropy of melting. The foundation of the chemical homology concept is revised, and the difficulties for extending the method to correlate and predict melting properties of ILs are presented. Despite the difficulties, the homology concept can still be used with some conditions and limitations that are analyzed in this article. Several correlations are proposed.     

Analytical Chemistry — today''s definition and interpretation

Conclusions Today Analytical Chemistry requires a broader definition than that concerned with its classical concept, objectives and methodology. The new concept of sample as a condensation of information of analytical interest has to be considered, as well as the increasing amount of instrumentation and metrology (physics) and data processing (applied mathematics; chemometrics) which are part of the present holistic definition of the subject. This is because the actual goals and constantly growing new objectives which today's Analytical Chemistry has to face and accomplish, are bound to a preliminary, strategic overview of the analytical problem (which often means much more than a simple sample). This problem has to be solved by the sensible, tactical application of the most suitable analytical method(s), worked out by Analytical Chemistry, the mother science of its instrument, chemical analysis.     

关于国防军工化学计量服务军队的思考

介绍国防军工化学计量为军队提供量值传递和溯源服务的现状,分析了军事化学计量面临的主要困难。系统阐述了国防军工化学计量体系构成,并对其化学计量能力进行了分析,提出了为基层军队提供计量服务的思路。国防军工化学计量在标准装置、技术规范、计量器具、技术研发等方面建立了完善的计量体系,具备参数结构全,地域覆盖广等优势,可作为军事化学计量体系的补充和发展,能更好地促进军队的建设和发展。     

HRTEM image simulations for the study of ultrathin gate oxides.

We have performed high resolution transmission electron microscope (HRTEM) image simulations to qualitatively assess the visibility of various structural defects in ultrathin gate oxides of MOSFET devices, and to quantitatively examine the accuracy of HRTEM in performing gate oxide metrology. Structural models contained crystalline defects embedded in an amorphous 16-A-thick gate oxide. Simulated images were calculated for structures viewed in cross section. Defect visibility was assessed as a function of specimen thickness and defect morphology, composition, size, and orientation. Defect morphologies included asperities lying on the substrate surface, as well as "bridging" defects connecting the substrate to the gate electrode. Measurements of gate oxide thickness extracted from simulated images were compared to actual dimensions in the model structure to assess TEM accuracy for metrology. The effects of specimen tilt, specimen thickness, objective lens defocus, and coefficient of spherical aberration (Cs) on measurement accuracy were explored for nominal 10-A gate oxide thickness. Results from this work suggest that accurate metrology of ultrathin gate oxides (i.e., limited to several percent error) is feasible on a consistent basis only by using a Cs-corrected microscope. However, fundamental limitations remain for characterizing defects in gate oxides using HRTEM, even with the new generation of Cs-corrected microscopes.     

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.     

基于化学的“化学测量学与技术”新工科专业建设建议

The background of the establishment of "chemistry metrology and technology" as an emerging engineering education major based on chemistry is analyzed. Based on the national development strategy, aiming at the urgent demand of interdisciplinary talents for the rapid development of chemistry metrology and technology, the necessity of setting up the major of "chemistry metrology and technology" based on chemistry is demonstrated. Based on the investigation of professional talents in instrument development enterprises and application fields, some suggestions on the program of "chemistry metrology and technology" major including orientation, objectives, graduation requirements and professional training are provided. Some requirements of the curriculum, teaching staff and teaching conditions are put forward.     

Comparability and recognition of chemical measurement results – an international goal

As a consequence of the globalisation of trade and industry and other human activities, reliability of and confidence in measurement results is increasingly required, also in the field of chemical analysis, so that measurements made in one country will be accepted in other countries without the necessity to repeat them. The prerequisite for confidence is comparability on the basis of known uncertainties which in turn are based on traceability to recognised references. Traceability structures for chemical measurements are required which, by providing calibration means traceable to national standards, allow uncertainty statements to be made at field level, thus establishing comparability. Such traceability structures are now being developed in all industrialised countries. To ensure international comparability, mutual recognition of the national activities in metrology in chemistry is required in addition. The Mutual Recognition Agreement (MRA) for national measurement standards and calibration certificates issued by national metrology institutes, which is currently under way within the framework of the Metre Convention, aimes at providing the necessary international confidence for all kinds of measurements. The field of chemical analysis is included in the international metrological infrastructure through the new Consultative Committee for Amount of Substance (CCQM). Carefully selected key comparison measurements, which cover the most important areas where traceability is required, and which are carried out by national metrology institutes in cooperation with other national institutes entrusted with the provision of part of the national references for chemical measurements, form the basis for declarations of equivalence under the MRA. The results of the first key comparisons and studies carried out so far clearly show that the group of laboratories involved in the key comparisons is capable of establishing the international references (key comparison reference values) for chemical measurements with sufficient accuracy, also in complicated matrices.     

What contribution can be made to biological monitoring by hair analysis

Summary The specific problems of sampling and sample preparation are presented here. The interpretation of sample comminution is discussed, the difficulties of the interpretation of hair analysis are pointed out, ending with consideration of the information available from hair analysis as opposed to that from the analysis of other types of sample and where its limits lie. The application and relevance of hair analysis in industrial medicine today is illustrated and discussed on the basis of several examples from clinical chemistry.Based on a lecture delivered to the working circle Analysen in biologischem Material — Deutsche Forschungsgemeinschaft Bonn, in Giessen, 16. October 1989     

An Overview of Analytical Chemistry in Australia

ABSTRACT

A brief overview of analytical chemistry research in Australia is presented and reference is made to the work of several research groups. Topics covered include the development of a longitudinally modulated cryogenic system for comprehensive gas chromatography, mixed-mode capillary electrochromatography for manipulation of separation selectivity of inorganic ions, new developments in chemical metrology, discontinuous flow analysis and its applications, the design and applications of an orthogonal acceleration time-of-flight mass spectrometer, and the use of chemiluminescence in a range of analytical techniques.     

An international intercomparison for 19-norandrosterone in human urine: the Comité Consultatif pour la Quantité de Matière (CCQM) Pilot Study CCQM-P68

Under the auspices of the Comité Consultatif pour la Quantité de Matière (CCQM) a laboratory intercomparison, CCQM-P68, was co-ordinated by the National Measurement Institute of Australia (NMIA) in 2005 involving the analysis of the steroid 19-norandrosterone (19-NA) in human urine. 19-NA is the major metabolite of nandrolone, a commonly abused anabolic agent. It is routinely tested by many sports drug testing laboratories and several national metrology institutes have developed reference methods to provide reference values for the certification of reference materials. The material distributed for the intercomparison was a freeze-dried human urine candidate reference material containing 19-NA at a level close to the allowed World Anti-Doping Agency (WADA) cut-off for this anabolic agent, i.e. 2 ng/ml. Four national/designated metrology institutes participated in the intercomparison and their results for this complex analysis were in excellent agreement, with a relative standard deviation (RSD) of only 1.7%. The expanded uncertainties at the 95% level of confidence for the reported results ranged from 3.7 to 7.0% at the 2.15 ng/g level.     

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.     

基于化学的新工科专业——“智慧分子工程”专业建设思路及建议

According to the construction concept of the "emerging engineering education", ideas and the connotations for constructing "intelligent molecular engineering" are introduced. The necessities of setting up of "intelligent molecular engineering" are discussed and the cultivation demand of professional talents is analyzed. The construction draft of "intelligent molecular engineering" is also expounded, including the cultivation targets and requirements of graduation, the teaching content of curriculum system, teaching staff and teaching conditions. All the statements are significant for guiding the design and construction of "intelligent molecular engineering".     

The deferred standard method–a technique for quantitative analysis in laboratory and process HPLC

Among the methods of quantitation commonly used in chromatography, the internal standard may be considered as the most useful and accurate; however, use of internal standards in liquid chromatography with UV and fluorometric detectors runs into considerable difficulties because the response factors may differ from each other by several orders of magnitude. Under these conditions, the search for an IS with a response factor similar to that of the analyte and adequately resolved from other peaks may prove very tedious. The deferred standard concept, already used in process and laboratory gas chromatography, is proposed as a solution; its definition, details of instrumentation, operation, and results are described in this paper. The material presented demonstrates its ability to solve this specific problem. In addition, use of the deferred standard approach is seen to save time and money.     

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)     

A practical approach to metrology in chemistry and biology

 The inherent difficulties of measurement in chemistry and biology have made it necessary to open discussion forums solely devoted to bench level work. This contribution summarises the conclusions of the Standards, Measurements and Testing Project (SMT4-CT96-6505) of the European Commission, devoted to the application of metrology in chemistry and biology. The objective of this project was to provide orientations and some recommendations which could partially satisfy end-users needs in the near future. Received: 29 September 1998 · Accepted: 21 December 1998     

The metrology of spectral analysis of disperse substances and materials

At present, a new scientific area in physical and chemical procedures of analysis, the metrology of analysis of substances and materials, has rapidly gained momentum. One of the main objectives of this research area is to obtain true information about the chemical composition of objects being analysed. Here under the correctness of an analysis we understand the quantity|?- C|. This quantity is used as a measure to establish the correspondence between the true element content C and its estimate ? obtained from a series of measurements, where

As the true element content serves its concentration determined in a standard sample. This defines the role attached to standard samples in such investigations.This paper presents some results of recent investigations carried out by the author and his co-workers in an attempt to solve the problem of obtaining standard reference materials (SRM) needed to test the correctness of and assess the techniques for spectral analysis of multicomponent substances and materials.