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1.
A case study is presented for the establishment of traceability for ammonium nitrogen determination in wastewater in a routine laboratory in order to fulfil the requirements of ISO/IEC standard 17025. The necessary relevant information was obtained from the method validation data, the quality control data and equipment calibration certificates. The method of measurement is described together with the measurement equation, selected traceable reference standards and the associated measurement uncertainty. The major sources of uncertainty of the result of measurement were identified and the combined uncertainty was calculated. Identification of the main uncertainty sources represents the basis for target operations for reducing the measurement uncertainty of this determination. 相似文献
2.
Dave Armbruster 《Accreditation and quality assurance》2009,14(7):393-398
A goal of clinical laboratory science is to produce accurate and comparable patient test results for a specimen independent
of analytical methodology. The In Vitro Diagnostics Directive in Europe has provided the impetus for the U.S. in vitro diagnostic
(IVD) industry to adapt the concepts of Metrology, the science of measurement, including measurement traceability and measurement
uncertainty. The joint committee for traceability in laboratory medicine has provided a valuable database of internationally
recognized reference materials and methods and reference laboratories. Much of the responsibility for measurement traceability
falls on IVD manufacturers, but all global stakeholders, including the clinical laboratory profession, government Regulatory
bodies, metrology institutes, and the providers of EQA/PT surveys, must cooperate to progress toward this goal. The adaptation
of the concepts of Metrology to the clinical laboratory is an appropriate and logical development and it will continue in
the twenty-first century. 相似文献
3.
A traceability protocol to the SI by gravimetric analysis 总被引:1,自引:0,他引:1
Charles M. Beck II 《Accreditation and quality assurance》1998,3(12):482-484
An example is presented of a traceability protocol for the measurement of a single-element strontium reference material solution,
executed by a "primary" method of measurement for certification. The method of measurement is briefly described together with
the measurement equation and the associated calculations for the estimation of uncertainties. This is followed by a discussion
and estimate of each component of uncertainty associated with the measurement, together with a final estimate of uncertainty.
The final estimate of uncertainty compares well with observed uncertainties for two previous laboratory measurements of the
reference material.
Received: 21 February 1998 · Accepted: 17 August 1998 相似文献
4.
Mirella Buzoianu 《Analytical and bioanalytical chemistry》1998,360(3-4):479-485
In order to provide quality assurance in the field of clinical chemistry, required by European Standards, the Romanian national
metrological infrastructure has to be improved. The main objectives of this important activity are metrological assurance
of concentration measurements, the assessment of the uncertainty, and the traceability of measurements. Within this framework,
reference materials play an important role. The experience of INM in the preparation, certification and use of reference materials
and in metrological assurance of clinical laboratory measurements (especially when absorption photometric devices are used)
is described. The combined uncertainty associated with chemical preparation of these reference materials is estimated.
Received: 25 April 1997 / Revised: 8 July 1997 / Accepted: 12 July 1997 相似文献
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6.
Kaj Heydorn 《Accreditation and quality assurance》2008,13(4-5):217-222
The novel proposed definition of measurement result in the international metrology vocabulary requires a revision of standards and guidelines for proficiency testing (PT), and
a new approach to processing proficiency data is needed to test the ability of laboratories to present not only unbiased quantity
values, but reliable estimates of their uncertainty. Hence, an accepted reference value with the smallest possible uncertainty
is needed to ascertain the proficiency of laboratories reporting results with lower than average uncertainty. A strategy based
on the T-statistic is proposed leading to an accepted reference value that fully reflects the uncertainties reported by participants
in a PT scheme and permits calculation of E
n
numbers to distinguish whether or not measurement results are consistent with the accepted definition of the measurand. The strategy
is applied to PT data from a recent international laboratory intercomparison of uranium isotopic ratios. 相似文献
7.
André Henrion 《Accreditation and quality assurance》1998,3(3):127-130
Repeated subsampling or a hierarchical design of experiments combined with an analysis of variance (ANOVA) is demonstrated
to be a useful tool in the determination of uncertainty components in amount-of-substance measurements. With the reference
material of human serum as investigated here for total cholesterol, besides several in-laboratory sources of uncertainty,
a vial-to-vial effect which can be regarded as an off-laboratory source was found to be significant. This knowledge might
be essential when the material is used for calibration and for the self-assessment of a laboratory.
Received: 29 October 1997 · Accepted: 26 November 1997 相似文献
8.
H. Marchandise 《Fresenius' Journal of Analytical Chemistry》1993,345(2-4):82-86
Summary The accuracy of the result of a chemical analysis can be established most reliably when the laboratory has demonstrated its performance in analysing an internationally accepted certified reference material similar to the tested product. When different laboratories have ensured traceability to the same or to equivalent reference materials, their results should be fully compatible and mutually acceptable, provided the laboratories specify the uncertainty of their results. This paper shows that uncertainty is a simple and efficient means of quantifying quality. A method easily applicable by any laboratory is proposed for the determination of uncertainties [1–3]. 相似文献
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10.
Adriaan M. H. van der Veen Milena Horvat Radmila Milačič Tinkara Bučar Urška Repinc Janez Ščančar Radojko Jaćimović 《Accreditation and quality assurance》2001,6(6):264-268
A proficiency test (PT) was carried out to investigate the quality of laboratory results measuring trace elements in sewage sludge. The scheme relied on reference values, established through flame atomic absorption spectroscopy and instrumental neutron activation analysis. Within the framework of the project, ”Proficiency testing in Central and Eastern European Countries”, the measurements were done in parallel using induced coupled plasma mass spectrometry. This paper discusses the design of the PTS, the metrological concepts behind it and the way in which it was operated. The discussion includes the estimation of measurement uncertainty of the reference values obtained, homogeneity testing and its uncertainty evaluation, as well as all relevant quality assurance aspects. From the results, it can be concluded that all measurement methods involved agree within their respective uncertainties. Furthermore, it can be concluded that it is feasible to operate a proficiency test of trace elements in sewage sludge using reference values. The agreement between the reference values and the consensus values is satisfactory. 相似文献
11.
采用封闭酸溶电感耦合等离子体质谱(ICP-MS)法测定岩石样品,分别对47种元素的测量结果不确定度进行评定。通过分析测试方法和测量条件,得到测量结果的不确定度主要由样品称量、样品溶液定容和样品溶液中元素浓度测量引入。在实验室质控条件下,对各不确定度分量进行评定和计算,其中随机因素导致的不确定度采用期间精密度试验综合评价,即采用A类方法评定。共完成了16个岩石国家标准物质(GBW 07103~GBW 07123)47种元素测量结果的不确定度合成,并参照GB/T 6379.2-2004,建立了含量w与扩展不确定度U之间的关系模型,运用这一关系模型可得到测量结果的不确定度估计值,只要测量过程本身或所使用的设备未变化,就不需要再重复进行不确定度评估。 相似文献
12.
Four approaches for estimation of reference values and their respective uncertainties of characterisation were compared using
data from the recently finalised certified reference materials ERM-EC680k and ERM-EC681k, elements in plastics. Reference
values and uncertainties of characterisation were estimated as mean of laboratory means and their respective standard deviations,
using equal weights and the weighting procedure of Mandel–Paule. In addition, two approaches taking into consideration uncertainty
information reported by the participants, namely the consistency check and simulation procedure proposed by Cox for CCQM Key
comparisons and an approach suggested by Pauwels et al. (Accred Qual Assur 3:180–184, 2000) were used. No difference between
the equally-weighted and Mandel–Paule consensus means was observed and the reference value from the Cox approach was in all
cases within ±2 u
char of each consensus mean. Uncertainties varied between the three approaches. Uncertainties derived from equally-weighted mean
of means approach are on average 14% above uncertainties using the Mandel–Paule consensus mean, 36% above the uncertainties
estimated by Pauwels et al., and 54% above the uncertainties from the Cox approach. Robustness of the uncertainty estimation
against incorrect estimation of uncertainties was assessed. Assumption of a 50% uncertainty of the individual uncertainties
resulted in an uncertainty of 30% of the uncertainty of characterisation. Differences between the four approaches are negligible
for this dataset when combined with the uncertainty contribution from heterogeneity and stability as prescribed in ISO Guide
35.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
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A proficiency testing (PT) scheme is developed for comparability assessment of results of concrete slump and compressive strength determination. The scheme is based on preparing of a test portion/sample of a concrete in-house reference material (IHRM) at a reference laboratory (RL) in the same conditions for every PT participant. Therefore, in this scheme IHRM instability is not relevant as a source of measurement/test uncertainty, while intra- and between-samples inhomogeneity parameters are evaluated using the results of RL testing of the samples taken at the beginning, the middle and the end of the PT experiment. The IHRM assigned slump and compressive strength values are calculated as averaged RL results. Their uncertainties include the measurement/test uncertainty components and the components arising from the material inhomogeneity. The test results of 25 PT participants were compared with the IHRM assigned values taking into account both the uncertainties of the assigned values and the measurement/test uncertainties of the participants. Since traceability of the IHRM assigned values to the international measurement standards and SI units cannot be stated, local comparability of the results is assessed. It is shown, that comparability of the slump and compressive strength determination results is satisfactory, while uncertainty evaluation for slump results requires additional efforts. 相似文献
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Bertrand Lombard 《Accreditation and quality assurance》2006,11(1-2):94-100
Given the current interest in measurement uncertainty (MU) in food microbiology, in particular for laboratory accreditation
purposes, and the need to have harmonized reference documents specifically in that area at the international level, ISO is
conducting works to meet this need. An ISO Technical Specification (ISO/TS 19036) is being prepared on MU estimation for quantitative
determinations. A global approach has been chosen, based on the reproducibility standard deviation of the final result of
the measurement process. Three possibilities are envisaged for the estimation of the reproducibility standard deviation, in
a decreasing order of preference: The intra-laboratory standard deviation, the inter-laboratory standard deviation derived
from method validation, and the inter-laboratory standard deviation derived from proficiency testing.The uncertainty of qualitative
determinations is still under investigation, and will be covered by a separate ISO publication.
Presented at AOAC Europe/Eurachem Symposium March 2005, Brussels, Belgium 相似文献
17.
Yoshito Mitani Judith Velina Lara-Manzano Aaron Rodriguez-Lopez 《Accreditation and quality assurance》2008,13(7):421-426
According to the experience of the successful implementation of proficiency tests (PT) by using the certified reference value
as the assigned value, a new scheme of evaluation is presented by suggesting the use of the uncertainty associated with the
certified value. The technical performance of laboratories is evaluated by the parameter quadratic mean error (QME), which
is the square root of the sum of the square of the bias and that of the standard deviation of the laboratory. This parameter
is considered as the estimate of the measurement uncertainty of the laboratory and is compared to the uncertainty (U) associated with the certified value provided by an NMI. Considering that the calibration and measurement capability, known
as the CMC, is recognized among NMIs, the ratio QME/U enables us to compare the PT relative to the CMC of an NMI, and, consequently, to any other comparison results based on the
CMC of signatories of the mutual recognition arrangement (MRA) of the International Committee of Weights and Measure (CIPM).
Presented at BERM-11, October 2007, Tsukuba, Japan. 相似文献
18.
Mario Plebani 《Accreditation and quality assurance》2006,11(6):291-296
Quality specifications, the level of performance required to facilitate clinical decision-making, not only have a central role in quality management in clinical laboratories, but are also essential for assuring the interpretation and utilization of laboratory information by clinicians. Laboratory tests have been grouped into five categories and the most suitable ways to communicate quality specifications to clinicians have been proposed. In particular, for tests with a uni-modal distribution, decision limits should replace the traditional reference values. For tests with a bi-modal distribution, in addition to reference values, some flags based on the uncertainty of laboratory data, can be included in the report. For tests used in patients monitoring and in evaluating the response to therapy, the reference change value or the most effective threshold of the difference between two consecutive results should be indicated. For tests/test batteries that require interpretative comments, these should be added on a regular basis. Lastly, pre- and post-test counseling is mandatory for genetic testing.Presented at Quality 2005, 10th Anniversary Meeting in Antwerp, Belgium March 7th–8th, 2005. 相似文献
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20.
W. C. Cunningham 《Analytical and bioanalytical chemistry》2013,405(26):8615-8620
The Food and Drug Administration uses water activity behavior characteristics when adjusting test portion mass to correct for the moisture condition of its cocoa powder in-house reference material. The cocoa powder’s moisture condition, and therefore weight, equilibrates according to the relative humidity (RH) of its surroundings. This process is predictable and defined by an isotherm. The reference values in the certificate of analysis are relative to the material’s condition at 30 % RH, which is assumed to be mid-range for typical laboratory settings. Since mass variations are relatively small within a 15–50 % RH range, the mass may be measured immediately after removing a test portion from a storage bottle and used without correction if a standard uncertainty of 0.7 % is acceptable for the mass. If greater accuracy is needed and the laboratory RH is known, a very simple and quick procedure can be used whereby the test portion is left open and exposed to the laboratory air overnight before weighing. After applying a correction, the standard uncertainty for mass measurement drops to 0.3 %. Figure
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