共查询到20条相似文献,搜索用时 82 毫秒
1.
Steps which are taken to implement the concept of measurement uncertainty in analytical chemical laboratories should take
full account of existing internationally agreed protocols for analytical quality assurance and reflect the needs of particular
analytical sectors. For the food sector this may mean that for official purposes the use of the term measurement uncertainty
is replaced by the term measurement reliability and that a quantitative estimation of this is made based on existing collaborative
trial data. In many analytical sectors, the differing strategies currently followed for the determination and use of recovery
information are an important cause of the non-comparability of analytical results. Guidelines which are being prepared for
the estimation and use of recovery information in analytical measurement may provide a more unified approach which includes
measurement uncertainty as a key concept in the use of recovery data.
Received: 4 November 1997 · Accepted: 3 February 1998 相似文献
2.
Bunthoon Laongsri Cheerapa Boonyakong Nongluck Tangpaisarnkul Chainarong Cherdchu 《Accreditation and quality assurance》2007,12(3-4):194-200
It has not been long that metrology is well accepted as an important part in analytical chemistry since it helps the chemists
to receive the best measurement and accurate results with traceability. The National Institute of Metrology Thailand (NIMT),
which is a public agency under the supervision of the Ministry of Science and Technology, not only focuses on physical standards
but also provides and maintains standards in chemical field. pH measurement is one of the most widely used in the laboratories
including industries and medical area in Thailand. The chemical laboratory starts working on the project with the objective
of disseminating an accurate result in routine pH measurement. In 2002, the laboratory provided a service in calibration of
pH meter and organized the first local interlaboratory comparison program (NIMT–C-ILC-1: pH buffer) in pH measurement. There
were three buffer solution samples in the range of acid, neutral, and base. A total of 44 laboratories participated in this
program. The NIMT chemical laboratory also participated in the proficiency testing program that was conducted by PSB Corporation
Testing Group in Singapore. In 2003, NIMT started research in preparation of secondary buffers by using highly accurate pH
meters with glass electrode systems. The laboratory produced three secondary buffers, which were pH 4.01, 6.86, and 9.18 with
uncertainty 0.020 pH at 25°C. The competence of the laboratory was shown by the measurement results of the pilot study (APMP.QM-P06),
which was organized by the APMP electrochemical analysis working group (EAWG/TCQM) in 2005. The title of this study was “pH
determination of two phosphate buffers by Harned cell method and glass electrode method”. NIMT aims to achieve for establishment
of the primary method for pH measurement in the near future.
Presented at -- “BERM-10” -- April 2006, Charleston, SC, USA 相似文献
3.
S. Duta Y. Aregbe L. Van Nevel P. Taylor F. Iacobescu 《Accreditation and quality assurance》2006,10(10):554-561
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. 相似文献
4.
Lauri Jalukse Irja Helm Olev Saks Ivo Leito 《Accreditation and quality assurance》2008,13(10):575-579
Accuracy data (expressed as precision and trueness) presented by the authors of three different micro modifications of the
Winkler titration procedure for dissolved oxygen concentration determination are critically evaluated. Tentative uncertainty
estimates are extracted from the data based on the single-laboratory validation approach (originally published in the Nordtest
Technical Report 537) and they lead to expanded uncertainty (k = 2) estimates in the range from 0.13 to 0.27 mg l−1 for the three procedures. It is demonstrated that, in all cases, the authors have presented the accuracy and/or precision
estimates of the procedures in a way that can lead to too optimistic conclusions about the uncertainty of their procedures.
This case study demonstrates the usefulness and flexibility of the single-laboratory validation approach to uncertainty estimation,
even in the case of insufficient data, and can be of interest to laboratory workers dealing with measurement procedures from
the literature. It is also expected to be of interest to university instructors of analytical chemistry and metrology in chemistry
as a real-life example of the critical evaluation of the literature data.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
5.
R. J. N. Bettencourt da Silva M. Filomena G. F. C. Camões João Seabra e Barros 《Accreditation and quality assurance》1998,3(4):155-160
Every analytical result should be expressed with some indication of its quality. The uncertainty as defined by Eurachem ("parameter
associated with the result of a measurement that characterises the dispersion of the values that could reasonably be attributed
to the, . . ., quantity subjected to measurement") is a good tool to accomplish this goal in quantitative analysis. Eurachem
has produced a guide to the estimation of the uncertainty attached to an analytical result. Indeed, the estimation of the
total uncertainty by using uncertainty propagation laws is components-dependent. The estimation of some of those components
is based on subjective criteria. The identification of the uncertainty sources and of their importance, for the same method,
can vary from analyst to analyst. It is important to develop tools which will support each choice and approximation. In this
work, the comparison of an estimated uncertainty with an experimentally assessed one, through a variance test, is performed.
This approach is applied to the determination by atomic absorption of manganese in digested samples of lettuce leaves. The
total uncertainty estimation is calculated assuming 100% digestion efficiency with negligible uncertainty. This assumption
was tested.
Received: 3 November 1997 · Accepted: 2 January 1998 相似文献
6.
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
7.
W. Jäger 《Accreditation and quality assurance》1997,2(4):199-202
The necessity for analytical quality assurance is primarily a feature of the analytical process itself. With the full establishment
of the EU domestic market, it is also becoming a legal necessity for an increasing number of analytical laboratories. The
requirements which laboratories will need to fulfil are stipulated in DIN EN 45 001. Accredited testing laboratories must
in fact provide evidence that they work solely in accordance with this standard. National and EU commissions, which are legislative
authorities, tend therefore to specify analytical methods, e.g. in the form of regulations or appendices thereto, intended
to ensure that results from different laboratories will be comparable and hence will stand up in a court of law. The analytical
quality assurance system (AQS), introduced by the Baden-Württemberg Ministry for the Environment in 1984, obliges laboratories
to regularly participate in collaborative studies and thereby demonstrate their ability to provide suitably accurate analyses.
This alone, however, does not sufficiently demonstrate the competence of a laboratory. Only personal appraisal of the laboratory
by an auditor, together with the successful analysis of a sample provided by the same and performed under his observation,
can provide proof of the competence of the laboratory. From an analytical point of view, the competence of a laboratory must
be regarded as the decisive factor. Competence can only be attained through analytical quality assurance, which thus must
be demanded of all laboratories.
Received: 4 October 1996 Accepted: 15 January 1997 相似文献
8.
Alex Williams 《Accreditation and quality assurance》2001,6(2):73-75
Establishment of the traceability and the evaluation of the uncertainty of the result of a measurement are essential in order
to establish its comparability and fitness for purpose. There are both similarities and differences in the way that the concepts
of traceability and uncertainty have been utilised in physical and chemical measurement. The International Committee of Weights
and Measures (CIPM) have only in the last decade set up programmes in chemical metrology similar to those that have been in
existence for physical metrology for over a century. However, analytical chemists over that same period have also developed
techniques, based on the concepts of traceability and uncertainty, to ensure that their results are comparable and fit for
purpose. This paper contrasts these developments in physical and chemical metrology and identifies areas where these two disciplines
can learn from each other. 相似文献
9.
Steluta Duta 《Accreditation and quality assurance》2000,5(6):243-249
For ensuring the traceability and uniformity of measurement results, the main objectives of national metrology programmes
in chemistry are to calibrate and verify measuring instruments, to evaluate the uncertainty of measurement results and to
intercompare the analytical results, etc. The concept of traceability has developed recently in chemical measurements, thus,
an attempt to implement the principles of metrological traceability especially by appropriateness calibration using composition
certified reference materials (CRMs) is underlined. Interlaboratory comparisons are also a useful response to the need for
comparable results. The paper presents some aspects and practices in the field of spectrometric measurement regarding the
metrological quality of the traceability by calibrating the instruments using suitable and reliable CRMs. The uncertainty
of results, as a measure of the reliability that can be placed on them, has been adequately described in different documents
and, as a consequence, some examples of evaluating the measurement uncertainty are described. The relationship between uncertainty
and traceability, as two fundamental concepts of metrology which are intimately linked, is underlined.
Received: 12 November 1999 / Accepted: 10 December 1999 相似文献
10.
S. L. R. Ellison 《Accreditation and quality assurance》1998,3(3):95-100
The possibility of using interlaboratory study repeatability and reproducibility estimates as the basis for measurement uncertainty
estimates is discussed. It is argued that collaborative trial reproducibility is an appropriate basis for estimating uncertainty
in routine testing provided certain conditions are met by the laboratory. The primary shortcomings relate to establishment
of traceability and consequent estimation of bias associated with the method, and quantitatively establishing the relevance
to the single laboratory. Approaches to resolving both difficulties are proposed, the former via full implementation of trueness
determination suggested in ISO 5725 : 1994 or by independent checks on individual accuracy and precision, the latter via a
reconciliation procedure. The paper also discusses other factors including sampling and sample pre-treatment, change in sample
matrix, and the influence of level of analyte.
Received: 28 October 1997 · Accepted: 17 November 1997 相似文献
11.
Stephan Küppers 《Accreditation and quality assurance》1997,2(7):338-341
The analytical chemists in process development in the pharmaceutical industry have to solve the difficult problem of producing
high quality methods for purity determination and assay within a short time without a clear definition of the substance to
be analyzed. Therefore the quality management is very difficult. The ideal situation would be that every method is validated
before use. This is not possible because this would delay the development process. A process-type quality development approach
with an estimation type fast validation (measurement uncertainty) is therefore suggested. The quality management process consists
of the estimation of measurement uncertainty for early project status. Statistical process control (SPC) is started directly
after measurement uncertainty estimation and a classical validation for the end of the project. By this approach a process
is defined that allows a fast and cost-efficient way of supporting the development process with the appropriate quality at
the end of the process and provides the transparency needed in the development process. The procedure presented tries to solve
the problem of the parallelism between the two development processes (chemical and analytical development) by speeding up
the analytical development process initially.
Received: 25 March 1997 · Accepted: 17 May 1997 相似文献
12.
Stoichiometry of analytical reactions is discussed as an important element of many primary methods (gravimetry, volumetry,
spectrophotometry, etc.) and therefore, of chemical metrology as a whole. Variations in stoichiometry caused by non-equilibrium
conditions, by changes in the reaction medium or by other factors can be a source of the dominant uncertainty component in
the analytical measurement. Such a situation is illustrated with the Karl Fischer (KF) reaction which is widely used in aquametry.
Two kinds of solvents used as a part of the reaction medium – alcohols and amides – are compared. The influence of the media
on the stoichiometry of the reaction and, correspondingly, on the titre of the KF reagent is evaluated.
Received: 4 November 1998 · Accepted: 22 December 1998 相似文献
13.
Phillips KM Wolf WR Patterson KY Sharpless KE Holden JM 《Analytical and bioanalytical chemistry》2007,389(1):219-229
Over a 6.5-year period a total of 2554 values were reported by nine laboratories for 259 certified or reference nutrient concentrations
in 26 certified reference materials (CRM) submitted to contract laboratories, blinded, as part of the qualifying process for
analytical contracts and in the routine sample stream as part of the National Food and Nutrient Analysis Program. Each value
was converted to a Z′-score, reflecting the difference from the assigned value related to the combined expected analytical uncertainty plus the
uncertainty in the CRM value. Z′-scores >|3.0| were considered unacceptable. For some nutrients (Na, folate, dietary fiber, pantothenic acid, thiamin, tocopherols,
carotenoids, monounsaturated, and polyunsaturated fatty acids), >20% of Z′-scores were >|3.0|. For total fat, vitamin C, and niacin >25% of Z′-scores were >|2.0|. Components for which CRM data were
best (more than 90% of Z′-scores <|2.0|) were Mg, P, Mn, Se, and vitamin B12. In some cases deviations from assigned values were not uniform across
laboratories and materials. For Na almost all high Z′-scores were for low-Na matrices, suggesting analytical problems related to concentration.
Figure Z′-scores for vitamins in certified reference materials
Disclaimer: Certain commercial equipment, instruments, or materials are identified in this paper in order to specify the experimental
procedure adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute
of Standards and Technology, or the United States Department of Agriculture, nor is it intended to imply that the materials
or equipment identified are necessarily the best available for the purpose. 相似文献
14.
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
15.
A. Ríos D. Barceló L. Buydens S. Cárdenas K. Heydorn B. Karlberg K. Klemm B. Lendl B. Milman B. Neidhart R. W. Stephany A. Townshend A. Zschunke M. Valcárcel 《Accreditation and quality assurance》2003,8(2):68-77
The European Commission has supported the G6MA-CT-2000–01012 project on ”Metrology of Qualitative Chemical Analysis” (MEQUALAN),
which was developed during 2000–2002. The final result is a document produced by a group of scientists with expertise in different
areas of chemical analysis, metrology and quality assurance. One important part of this document deals, therefore, with aspects
involved in analytical quality assurance of qualitative analysis. This article shows the main conclusions reported in the
document referring to the implementation of quality principles in qualitative analysis: traceability, reliability (uncertainty),
validation, and internal/external quality control for qualitative methods.
Received: 15 October 2002 Accepted: 20 October 2002
This paper is a summary of the Quality Assurance section included in the final report of the MEQUALAN project. The authors
of this paper correspond to the members of the MEQUALAN Consortium. One of them (K.H.) does not fully agree with some parts
of the text.
Correspondence to A. Ríos 相似文献
16.
K. Heydorn 《Journal of Radioanalytical and Nuclear Chemistry》2000,244(1):7-15
For more than half a century we have been using activation of stable isotopes to determine chemical elements, and significant contributions have been made to a variety of scientific subjects. Nevertheless, activation analysis has not yet become integrated in the field of chemical analysis, and therefore the special features characteristic of activation analysis have not been fully realised in analytical chemistry. At the same time basic chemical knowledge has only to a limited extent been utilised in the development of analytical methods based on activation. This situation has only now become painfully clear, when a world-wide requirement is being made to express the uncertainty of analytical results in accordance with the BIPM philosophy. The identification and estimation of all uncertainty components needed to produce a reliable uncertainty budget requires the combined efforts of all parties. An attempt is here made to extrapolate current trends for the expression of uncertainty in activation and analysis into the future and to show, how the implementation of the BIPM Guidelines with respect to correction for all known or suspected biases, achievement of statistical control, and full traceability, can help bringing analytical chemistry into its rightful position as a scientific discipline in the field of metrology. 相似文献
17.
H. Hey 《Accreditation and quality assurance》1998,3(5):211-214
In order to ensure food consumer protection as well as to avoid barriers to trade and unnecessary duplications of laboratory
tests and to gain mutual recognition of results of analyses, the quality of laboratories and test results has to be guaranteed.
For this purpose, the EC Council and the Commission have introducedprovisions
– on measures for quality assurance for official laboratories concerning the analyses of foodstuffs on the one hand and animals
and fresh meat on the other,
– on the validation of test methods to obtain results of sufficient accuracy.
This article deals with legal requirements in the European Union on basic principles of laboratory quality assurance for official
notification to the EC Commission and on method validation concerning official laboratories. Widespread discussions and activities
on measurement uncertainty are in progress, and the European validation standards for official purposes may serve as a basis
for world-wide efforts on quality harmonization of analytical results. Although much time has already been spent, definitions
and requirements have to be revised and further additions have to be made. 相似文献
18.
John L. Love 《Accreditation and quality assurance》2002,7(3):95-100
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 相似文献
19.
Rainer A. Schmidt 《Accreditation and quality assurance》2001,6(4-5):178-180
There are many different means of demonstrating the quality of performance of an analytical laboratory. Proficiency testing
(PT) is just one! As in other analytical fields, interlaboratory comparisons play an important role in the chemical industry.
Collaborative trials or method performance studies do have a long tradition in this field. Sometimes they were designed as
laboratory performance studies with the clear aim of making analytical results comparable, e.g. petrol, coal, gas, noble metals
analyses – not to mention the biggest PT scheme run on a daily world-wide basis – trade itself. All this is an ongoing process,
which started long before the idea of assessing and accrediting the performance of analytical laboratories was born. However,
when striving for accreditation in 1996, the analytical production laboratories of the Chemicals Business Unit of the Bayer
AG in Germany implemented another facet of PT schemes. In-house-PT schemes are performed regularly and turned out to be useful
in evaluating, monitoring, and thus improving, the quality of routine analytical work.
Received: 5 December 2000 Accepted: 15 January 2001 相似文献
20.
M. Gra?a Dias M. Filomena Cam?es Luísa Oliveira 《Accreditation and quality assurance》2012,17(2):183-189
For consistent interpretation of an analytical method result it is necessary to evaluate the confidence that can be placed
in it, in the form of a measurement uncertainty estimate. The Guide to the expression of Uncertainty in Measurement issued
by ISO establishes rules for evaluating and expressing uncertainty. Carotenoid determination in food is a complex analytical
process involving several mass transfer steps (extraction, evaporation, saponification, etc.), making difficult the application
of these guidelines. The ISO guide was interpreted for analytical chemistry by EURACHEM, which includes the possibility of
using intra- and interlaboratory information. Measurement uncertainty was estimated based on laboratory validation data, including
precision and method performance studies, and also, based on laboratory participation in proficiency tests. These methods
of uncertainty estimation were applied to analytical results of different food matrices of fruits and vegetables. Measurement
uncertainty of food carotenoid determination was 10–30% of the composition value in the great majority of cases. Higher values
were found for measurements near instrumental quantification limits (e.g. 75% for β-cryptoxanthin, and 99% for lutein, in
pear) or when sample chromatograms presented interferences with the analyte peak (e.g. 44% for α-carotene in orange). Lower
relative expanded measurement uncertainty values (3–13%) were obtained for food matrices/analytes not requiring the saponification
step. Based on these results, the saponification step should be avoided if food carotenoids are not present in the ester form.
Food carotenoid content should be expressed taking into account the measurement uncertainty; therefore the maximum number
of significant figures of a result should be 2. 相似文献