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1.
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
2.
A metrological approach to determination of the chromatographic purity of obidoxime chloride and the corresponding obidoxime
chloride reference material (RM) with a certified chromatographic purity value have been developed. This value was defined
as the ratio of the sum of peak areas of obidoxime chloride isomers to the total peak area of detected substances including
impurities (%) under specified HPLC–UV conditions. The RM homogeneity and stability were studied using HPLC with UV detection
and evaluated as satisfactory. The certified value calculated from the results of an interlaboratory trial was equal to 99.9%
with the expanded uncertainty of 0.6% at the level of confidence 0.95 and the coverage factor 2. The RM certified value, like
other results of chromatographic purity determination traceable to the reference measurement procedure, is not traceable directly
to the SI mole. However, the results are comparable in metrologically traceable environments, i.e. when relevant measuring
laboratory instruments are calibrated with traceability chains to the corresponding SI units. Therefore, the RM can be used
as a measurement standard (calibrator) for analytical instruments and as a control sample for quality control of HPLC obidoxime
chloride assay results. 相似文献
3.
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
4.
In continuing their attempt to bring general issues concerned with trustworthy chemical measurements to review and international
discussion, the authors propose basic aims and requirements for protocols of chemical-measurement procedures with traceability
to the SI or, where this is not possible, to units of internationally recognized measurement scales. Documents describing
such protocols could be useful in science, technology, law, or trade. Concepts and definitions for protocols have been introduced
in Part I of this contribution. Part II here deals with the development and application of protocols for intended in-laboratory,
commercial, national, or international recognition. Protocols deal with measurement methods, instrumentation, and the estimation
of uncertainties from all possible sources of measurement errors. Uncertainties define the quality of all links in a traceability
chain starting from the value of a measurand in a sample, often through a certified value in a reference material, either
to the SI, or – if this is not possible – to a value on a suitable, internationally agreed measurement scale. A protocol may
concern itself with the complex interplay between uncertainties, tolerances, and any limit values introduced by the set aims
of specific measurements.
Received: 23 April 1997 Accepted: 27 April 1997 相似文献
5.
For accurate measurement of concentrations of substances by instrumental analysis, reliable calibration standards are needed.
In Japan, national reference materials are supplied under the national standards dissemination system named the Japan Calibration
Service System (JCSS). In JCSS, calibration standards for the analysis of environmental pollutants are supplied. For the traceability
to the SI of reference materials for calibration in JCSS, the National Metrology Institute of Japan (NMIJ) is developing high-purity
reference materials of volatile organic compounds (VOCs) as NMIJ CRMs. The freezing-point depression method, which has potential
as a primary method of measurement, is employed for the determination of property value. In this paper, a development scheme
of certified reference materials of high-purity VOCs is described.
Presented at BERM-11, October 2007, Tsukuba, Japan. 相似文献
6.
Metrological designs of experiment for proficiency testing (PT) with a limited number of participants are discussed. The designs are based on development of in-house reference materials (IHRMs) with traceable assigned values and fit-for-purpose uncertainties, used in a PT scheme as the measurement standards. When adequate certified reference materials (CRMs) are available, a comparative approach for IHRM development, using simultaneous analysis of IHRM and CRM test portions in pairs, is proposed for PT objectives. In the case where adequate CRMs are not available – for example, in the field of analysis of unstable aqueous systems – the function of the measurement standard for PT can be fulfilled by a synthetic IHRM prepared gravimetrically using non-adequate, non-aqueous CRMs or pure substances. The CRM or the pure substance is used as a spike for fortification of a natural water sample, while the natural water sample is used as a working IHRM for the spike determination. In this case the traceability chain is longer, since two IHRMs are added for one quantity determination, but it remains unbroken.Presented at the Second International Conference on Metrology –Trends and Applications in Calibration and Testing Laboratories, 4–6 November 2003, Eilat, Israel 相似文献
7.
Until quite recently, Australia has not been much involved in the preparation and certification of matrix reference materials for chemical testing. Even today, the vast bulk of chemical reference materials used in Australia are imported from other world producers. Increased international focus on the accuracy, traceability and comparability of chemical measurements has led to the establishment of the National Analytical Reference Laboratory (NARL) within the Australian Government Analytical Laboratories. Part of the work of NARL will be to supply matrix reference materials, not available from existing sources, to meet specific Australian requirements. This need has been addressed in the past by a combination of industry and government initiatives. Examples include a series of certified matrix reference materials for chemical testing of iron ore, coal and mineral sands produced by Standards Australia and a series of three animal fat matrix reference materials certified for a range of pesticide residues produced by the Australian Chemical Standards Laboratory (now part of NARL). To make effective use of limited resources, it will be important for NARL to focus on identified priorities and to maximise the use of available Australian resources and expertise through technical collaboration for reference material production. An important part of this process should be input on needs and priorities from reference material "users" such as government legislators, regulatory authorities, standards setting bodies, industry and the analytical community. The aim will be to produce matrix certified reference materials that are traceable to SI or other international standards at a stated level of measurement uncertainty. 相似文献
8.
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
9.
A discussion of proficiency testing (PT) topics started by Heydorn (Accred Qual Assur 15:643–645, 2010) is continued in the present paper. The role of PT in the accreditation of testing/analytical laboratories, the use of consensus
values (average or weighted average, median, observed standard deviation, etc.) and a metrological background of PT schemes
are discussed. It is shown that metrological traceability, comparability, and compatibility, as well as commutability of a
reference material, are the key issues of any PT scheme that applies certified reference material as test items. Metrological
compatibility of PT results in such schemes is a property demonstrating the closeness of the PT results to the certified value
in comparison with the measurement uncertainty of their difference. The metrological background is especially important for
the selection and use of PT schemes for a limited number of participants (fewer than 30) as detailed in IUPAC/CITAC Guide
on the topic published in 2010 in Pure Appl Chem 82(5):1099–1135. 相似文献
10.
If the value of a derived measurement standard is assigned by comparison with a reference standard of the same quantity,
the uncertainty is increased by the additional uncertainty on the difference measurement. This basic fact has lead to the
general belief that the uncertainty of derived standards is always larger than that of the reference standards. However, if
the value of a derived standard is assigned by comparison with several independent reference standards using an appropriate
average, the increase of uncertainty due to the uncertainty on difference measurement may be counterbalanced by the the well-known
decrease of uncertainty through averaging. The gain of accuracy made possible by this mechanism is restricted to second-generation
standards. Further gain through iteration is prevented by correlation between standards derived from the same set of reference
standards. As a consequence, the concept of metrological hierarchy levels, relating to traceability chains, becomes questionable
for traceability networks. 相似文献
11.
Results that reference SI units rarely pose problems in chemical measurement because traceable standards, with uncertainties derived from a chain of calibrations from the SI, are readily available at the analyst??s bench. These uncertainties are nearly always far smaller than that required for fitness for purpose in the analytical result. Moreover, the greater part of the uncertainty in a typical result is not derived from primary measurements traceable to the SI but from recovery problems and matrix effects. Even so, the incidence of wildly inaccurate results stems not from this uncertainty but from ??blunders??, deviations from the correct procedure. Attention to traceability beyond that employed by any competent analyst therefore cannot reduce the uncertainty. Furthermore, there is no rational reason to reduce the uncertainty if the result is already fit for purpose. The current focus on traceability is distracting analysts from the more pressing task of eliminating blunders. 相似文献
12.
The 2002 IUPAC recommendation on pH (provisional) has taken its own philosophy to provide a basis for comparable and traceable assignment of a value, from a measurement, to the quantity pH. Whereas the substituted 1983 IUPAC recommendation relied heavily on precisely prescribed experimental techniques and procedures, the current recommendation defines a hierarchical relationship between references for comparison (primary and secondary standards) and objective criteria on the comparison of measurements with these standards. The recommendation aims at a traceability chain from the national metrological institution (NMI) level down to field and laboratory measurements. Currently, however, the traceability chain is developed to the level of certified reference materials (CRM), namely the above mentioned primary and secondary standards. To complete the traceability chain, several theoretical and practical aspects have to be pondered. In part, the methods for comparative assessment of different options have yet to be developed. As an illustrating example of the complexity of issues to be considered in a further extension of the traceability chain is estimation of the doubt associated with Pitzer coefficients. The Pitzer equations for activity coefficient modelling are explicitly mentioned in the 2002 IUPAC recommendation on pH (provisional) as enabling possible improvement in the ionic strength extrapolations to zero ionic strength. An assessment of uncertainty of ternary Pitzer coefficients is given for the first time. 相似文献
13.
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
14.
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. 相似文献
16.
ISO 9000 series strictly requires traceability to national or international measurement standards. It is becoming more necessary
to make clear the concept of traceability of measurement standards with respect to chemical composition and to accredit the
reference material producers. In Japan, the accreditation system for reference material producers is considered to satisfy
the requirement of ISO Guide 34, ISO 9000 series and ISO/IEC Guide 25, while the producer fulfills the concept of traceability
of measurement standards. This paper describes the production of iron and steel reference materials in Japan relating to the
international standardization of methods (written standards) and accreditation of reference material producers.
Received: 11 October 1996 Accepted: 5 December 1996 相似文献
17.
Since the uncertainty of each link in the traceability chain (measuring analytical instrument, reference material or other
measurement standard) changes over the course of time, the chain lifetime is limited. The lifetime in chemical analysis is
dependent on the calibration intervals of the measuring equipment and the shelf-life of the certified reference materials
(CRMs) used for the calibration of the equipment. It is shown that the ordinary least squares technique, used for treatment
of the calibration data, is correct only when uncertainties in the certified values of the measurement standards or CRMs are
negligible. If these uncertainties increase (for example, close to the end of the calibration interval or shelf-life), they
are able to influence significantly the calibration and measurement results. In such cases regression analysis of the calibration
data should take into account that not only the response values are subjects to errors, but also the certified values. As
an end-point criterion of the traceability chain destruction, the requirement that the uncertainty of a measurement standard
should be a source of less then one-third of the uncertainty in the measurement result is applicable. An example from analytical
practice based on the data of interlaboratory comparisons of ethanol determination in beer is discussed.
Received: 5 October 2000 Accepted: 3 December 2000 相似文献
18.
Characterization of in-house reference materials (IHRMs) with traceable property values for the mometasone furoate assay is discussed. The traceability of the value carried by the IHRM has been established to the value carried by a higher metrological status United States Pharmacopoeia Reference Standard (USP RS). A comparative approach is used to overcome systematic errors in measurement results, specific to the measurement method and/or to the laboratory developing the IHRM. The traceability chain was realized by the simultaneous analysis of the IHRM and the USP RS test portions under the same conditions. 相似文献
19.
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
20.
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
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