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1.
P. de Bièvre Robert Kaarls H. Steffen Peiser Stanley D. Rasberry William P. Reed 《Accreditation and quality assurance》1997,2(4):168-179
The authors propose definitions and terminology for protocols on traceability links, generally to the international system
of units, for specific chemical-analytical measurements in accordance with recognized principles of science. These definitions
and terms could be useful in science, technology, commerce or law. A chain of such links leads from a measurand in a sample
up to a unit in the International System of Units or, if unavailable, to a value on an internationally recognized measurement
scale. The quality of such a chain is quantified by combining all recognized uncertainties estimated for all its links. These
uncertainties of the measured values arise from many potential error sources. The protocols should give details of specific
uses of reference materials, measuring instruments and standard measurement methods.
Received: 12 January 1997 Accepted: 31 January 1997 相似文献
2.
W. Richter 《Accreditation and quality assurance》1997,2(8):354-359
Primary methods of measurement have a central function in metrology. They are an essential component in the realisation of
the SI units and therefore are indispensable for establishing traceability of measurements of all kinds of physical quantities
to the corresponding SI units. This is also true for chemical analysis. Gravimetry, titrimetry, coulometry, and isotope dilution
mass spectrometry (IDMS) are evaluated with regard to their potential to be primary methods according to a general definition
of primary methods recently given by the Comité Consultatif pour la Quantité de Matière (CCQM). Optical absorption spectrometry
and methods based on colligative properties are also considered. A general scheme for establishing traceability of chemical
measurements to the SI units using primary methods is discussed.
Received: 17 April 1997 · Accepted: 9 August 1997 相似文献
3.
G. Price 《Accreditation and quality assurance》1996,1(2):57-66
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 相似文献
4.
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. 相似文献
5.
6.
R. Dybkaer 《Accreditation and quality assurance》2001,6(1):16-19
The medical laboratory must provide results of measurements that are comparable over space and time in order to aid medical
diagnosis and therapy. Thus, metrological traceability, preferably to the SI, is necessary. The task is formidable due to
the many disciplines involved, the high production rate, short request-to-report time, small sample volumes, microheterogeneity
of many analytes, and complex matrices. The prerequisite reference measurement systems include definition of measurand, unit
of measurement (when applicable), consecutive levels of measurement procedures and calibrators in a calibration hierarchy,
international organizations, reference measurement laboratories, dedicated manufacturers, written standards and guides for
the medical laboratory, production of reference materials, internal and external quality control schemes, and increasingly
accreditation. The present availability of reference measurement procedures and primary calibrators is shown to be insufficient
to obtain international comparability of all types of quantity in laboratory medicine.
Received: 19 April 2000 / Accepted: 3 July 2000 相似文献
7.
T. Catterick D. Craston B. King R. F. Walker K. S. Webb 《Accreditation and quality assurance》1999,4(1-2):3-13
The UK Valid Analytical Measurement Programme has pump-primed developments in chemical metrology, through a major project
on reference methodology and reference materials. This paper provides an overview of developments during 1994–1997 and covers
work on primary methods for trace inorganic and trace organic analysis, including the use of isotope dilution mass spectrometry;
studies of sample pre-treatment, including digestion, extraction, and separation aimed at improving this weak link in the
traceability chain; prioritisation, production and marketing of both pure substance and matrix reference materials; and international
collaboration concerned with interlaboratory comparisons and the development of concepts, terminology and systems to underpin
the international chemical measurement system. References are given to a number of papers covering specific parts of the programme.
Received: 5 August 1998 · Accepted: 12 September 1998 相似文献
8.
P. De Bièvre 《Accreditation and quality assurance》2000,5(6):224-230
Traceability is a property of the result of a measurement. Since values carried by (reference) materials must also have been
obtained, of necessity, by measurement, the definition of traceability also applies to reference materials. It is extremely
helpful to give the traceability (of the origin) of a reference material a separate name, i.e. 'trackability'. An analysis
of the function of values carried by reference materials, shows that they can fulfill different functions, depending on the
intended use. One of the functions located outside the traceability chain – and hence not very relevant for establishing traceability
– is evaluating the approximate size of the uncertainty of the measurement of an unknown sample by performing a similar measurement
on a reference material, used as a 'simulated sample'. Another function is located inside the traceability chain, where the
reference material is used as an added 'internal standard'. Then, the value carried by the reference material is essential
for establishing the traceability of the measured value of an unknown sample. In the latter application, the reference material
acts as an 'amount standard' (the certified value for amount is used).
Received: 11 November 1999 / Accepted: 24 February 2000 相似文献
9.
10.
Traceability to the System International (SI) is an important prerequisite for international comparability and uniformity
of chemical measurements to ensure mutual recognition of the results. In theory, all measurements can be traced back to the
seven base units of the SI. Although the traceability system works well for most physical measurements, in many analytical
and in some spectrophotometric measurements this system is not satisfactory. This paper describes the particular and practical
problems and the contribution of the Romanian National Institute of Metrology in this field. The paper discusses the following
concepts: clearly defined targets in the form of requirement specification, knowledge of trueness and/or measurement uncertainty,
and traceability through an unbroken chain of calibration to primary standards. Traceability and uncertainty being two concepts
inherently coupled, two examples of assessment of the uncertainty of measurement results are given for two spectrophotometric
methods currently used in chemical laboratories.
Received: 17 July 1996 Accepted: 2 September 1996 相似文献
11.
Marcellé Archer Betty-Jayne de Vos Maria S Visser 《Accreditation and quality assurance》2007,12(3-4):188-193
Internationally, certified ethanol reference materials are required to calibrate breathalysers and blood-alcohol measurement
instruments. The CSIR National Metrology Laboratory of South Africa provides certified aqueous ethanol solutions with traceability
to the SI. Ethanol solutions in the concentration range 10 mg/100 g to 20 g/100 g are prepared gravimetrically by mixing ethanol
and reagent quality water. To verify the concentration of the ethanol it is oxidized to acetic acid with potassium dichromate
in the presence of sulphuric acid. The unreacted potassium dichromate is back-titrated with sodium thiosulphate. The method
utilizes gravimetry and titrimetry, which are both primary methods. This paper addresses aspects of ethanol-certified reference
materials that have not been previously published: traceability, stability of unpreserved ethanol solutions, homogeneity,
quality control measures and the effect of reproducibility on the measurement uncertainty.
Presented at -- “BERM-10” -- April 2006, Charleston, SC, USA 相似文献
12.
A current interest in chemistry concerns traceability of analytical measurements to the International System of Units (SI) and the estimation of their uncertainties in accordance with principles of metrology, that is, measurement science. “Primary methods of measurement” achieve traceability to SI directly without intermediate reference standards or materials and without significant empirical correction factors. Isotope-dilution mass spectrometry should be regarded as such a method. It has the potential of smallest presently achievable uncertainties for analytical measurements directly or for the certification of reference materials including those with abnormal isotopic composition. A simple explanation of the method including its basic equations is given. Full uncertainty estimation is emphasized in terms of these equations. The wider use of concepts of metrology in chemistry is discussed. 相似文献
13.
Toshiaki Asakai Mariko Murayama Tatsuhiko Tanaka 《Accreditation and quality assurance》2007,12(3-4):151-155
The accuracy and uncertainty of the coulometric measurement results of reference materials for acidimetric titration were
examined in this study. The results for amidosulfuric acid and potassium hydrogen phthalate are presented. The uncertainty
was investigated by examining the dependency on the sample size and on the electrolysis current. Changes in the titration
parameters did not result in any significant effects on the titration results. Acidimetric standards with the certified value
linked to the SI were developed. In addition, the intercomparison of acidimetric standards was carried out by gravimetric
titration, and the relationship between our coulometric results was determined. Furthermore, due to recent internationalization,
not only the traceability to the SI but also the relationship and consistency of their analytical data have gained increasing
importance. Our results were validated using certified reference materials (CRMs) obtained from different National Metrology
Institutes (NMIs), and their relationships are presented.
Presented at -- “BERM-10” -- April 2006, Charleston, SC, USA. 相似文献
14.
I. Kuselman Alexander Weisman Wolfhard Wegscheider 《Accreditation and quality assurance》2002,7(3):122-124
The traceability of in-house reference materials (IHRM) is discussed. It is shown that a systematic error in results of a
measured value, specific to a measurement method or to a laboratory developing an IHRM, can be overcome if a comparative approach
to IHRM characterization is used. A traceability chain of the value carried by the IHRM to the value carried by the reference
material with higher metrological status and sufficiently similar matrix (for example, a certified reference material – CRM
according to ISO Guide 30) is helpful in such a case. The chain is realized when the IHRM samples are analysed simultaneously
with the CRM samples under the same conditions. This and other traceability chains necessary for the IHRM development are
examined as the measurement information sources. 相似文献
15.
Heinrich Kipphardt Ralf Matschat Olaf Rienitz Detlef Schiel Wolfgang Gernand Dietmar Oeter 《Accreditation and quality assurance》2006,10(11):633-639
A complete metrological traceability system for measurement results of chemical analysis was set up. Core components are pure substances (national standards) characterised at the highest metrological level, primary solutions prepared from these pure substances and secondary solutions deduced from the primary solutions and intended for sale. The relative uncertainty of the element mass fraction of the primary substances and solutions is < 0.01 and < 0.05%, respectively. For the certification of transfer solutions and for stability testing, a precision measurement method for element contents has been developed by means of optical emission spectrometry (ICP OES) by which uncertainties between 0.1 and 0.05% can be achieved. The dissemination to field laboratories is effected with the aid of a calibration laboratory of the German Calibration Service (DKD) which certifies the element content of the secondary solutions with an uncertainty ≤ 0.3%. Calibration with these solutions enables the user to establish traceability of his measurement results to the International System of Units (SI). Currently, the system comprises Cu, Fe, Bi, Ga, Si, Na, K, Sn, W, and Pb. 相似文献
16.
ISO/IEC 17025 requires that testing laboratories establish the traceability of their measurements, preferably to the SI units of measurement. The responsibility for establishing traceability lies with each individual laboratory and must be achieved by following a metrological approach.The results of measurements made in such a way are traceable to the standards used in method validation and to the calibration standards used during the measurement process. If these standards are traceable to SI then the measurements will also be traceable to SI.Participation in appropriate proficiency studies (an ISO/IEC 17025 requirement) enables laboratories to demonstrate the comparability of their measurements. If the materials used for the studies have traceable assigned values, then proficiency testing also provides information about measurement accuracy and confirms, or otherwise, that appropriate traceability has been established. This paper will report on a new approach for the establishment of traceable assigned values for chemical testing proficiency studies. The work is conducted at a "fit for purpose" level of measurement uncertainty, with costs contained at a level similar to previous "consensus" based proficiency studies. By establishing traceable assigned values in a cost effective way, NARL aims to demonstrate the added value of the metrological approach to participant laboratories. 相似文献
17.
G. Price 《Accreditation and quality assurance》1998,3(2):82-83
The Analytical Division of the Royal Australian Chemical Institute (RACI) held its 14th biennial symposium on analytical
chemistry (14AC) in Adelaide, South Australia on 5–9 July 1997 [1]. The theme, "A broader view of the world" was an explicit
invitation from the organisers to analysts to "take time away from their laboratories and consider how their work affects
the world . . . A major challenge to chemists is to redefine their role in industry, education and the community and face,
head-on, the demands brought about by free trade, economic rationalism and the environment." Part of this challenge, as reflected
in invited plenary and keynote speakers as well as the cut and thrust of debate on the conference floor, is to address the
important role of chemical measurement and confidence in the domestic and international systems of measurement. 相似文献
18.
Anita Schmidt 《Accreditation and quality assurance》2001,6(6):277-278
The 5th Eurolab Symposium on 4th and 5th October in Edinburgh was the highlight event of Eurolab in 2000, Eurolab’s 10th anniversary
year. Under the title: ”Confidence in Testing Services – new expectations, new rules, new challenges” it reflected recent
changes and developments in the laboratory scene and focussed on new tasks and challenges. The most essential changes for
laboratories are connected with the new standard ISO/IEC 17025 ”General requirements for the competence of testing and calibration
laboratories”. Keywords in this respect are uncertainty of measurement and traceability to SI units, requirements on personnel,
proficiency testing, customer orientation, and management systems. 相似文献
19.
X. R. Pan 《Accreditation and quality assurance》1996,1(4):181-185
Traceability is an essential property of a measurement result. However, it is recognized that the results of chemical measurements
can be lacking in this property. In this paper we try to show how to understand and establish traceability in chemical measurement.
The traceability connotation and the necessity of tracing back to SI units are described by means of comparability well-known.
The roles and interrelationships of quality assurance, accreditation, calibration, reference material, analytical method,
comparison and uncertainty in establishing traceability are explained with the aid of a block diagram. The paper also includes
diagrams illustrating the Chinese situation and experience of establishing traceability for chemical measurement in China. 相似文献
20.
P Robouch M Eguskiza M I Maguregui S Pommé J Pauwels 《Fresenius' Journal of Analytical Chemistry》2001,370(2-3):255-258
The main concern of producers of certified reference materials (CRM) is the preparation of high-quality products with demonstrated homogeneity and stability, combined with a well established set of certified characteristics. CRM producers must, furthermore, comply with other constraints imposed by the ISO Guide 34: production processes, production control, and certification analyses should be performed by expert laboratories, using validated protocols documented in their respective quality assurance manuals; laboratory mean values and the corresponding "expanded" uncertainties, must be used for the determination of the certified values, as recommended by the ISO Guide to the Expression of Uncertainties in Measurements (GUM); and when possible, traceability of the certified value to the SI units, using appropriately validated and/or primary methods, must be ensured. k0-NAA, i.e. neutron activation analysis with k0 standardization, is one of the analytical techniques implemented at the Reference Material Unit of IRMM; it meets the first two requirements. 相似文献