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1.
Proficiency testing (PT) results have been used to improve traceability in chemical drinking water analysis. With a generalized
least-square regression the mass concentrations of As and Sb were calculated in a drinking water that had been used to prepare
proficiency testing samples by a spiking procedure. From the mass concentrations in the matrix and the spiked amounts, reference
values with an uncertainty budget could be calculated without the need for reference measurements. The degree to which these
reference values can be regarded as traceable is discussed. The results showed slight deviations in some samples between reference
values and consensus means. 相似文献
2.
Proficiency testing as a means of external quality assessment plays the role of independent evidence of laboratories’ performance.
To enable laboratories to fulfil the requirements stated in legislation, methodology for evaluation of laboratories’ performance
in proficiency testing schemes should incorporate principles of measurement results which are fit for intended use and incorporate
evaluation of laboratories’ performances based on independent reference value. A proficiency testing scheme was designed to
support Drinking Water Directive (98/83/EC) specifically. The methodology for performance evaluation, which takes into account
a “fitness for purpose”-based standard deviation for proficiency assessment, is proposed and discussed in terms of requirements
of the Drinking Water Directive. A ζ′-score, modified by application of target uncertainty was developed in a way that fulfils requirements defined in the legislation.
As an illustration, results are reported for nitrate concentration in water. The approach presented can also be applied to
other fields of measurements. 相似文献
3.
Comparability of analytical results obtained in proficiency testing based on a metrological approach
Ilya Kuselman 《Accreditation and quality assurance》2006,10(9):466-470
A “yes–no” type of criterion is proposed for the assessment of comparability of proficiency testing (PT) results when the PT scheme is based on a metrological approach, i.e. on the use of a reference material as the test sample, etc. The criterion tests a null hypothesis concerning the insignificance of a bias of the mean of the results from a traceable value certified in the reference material used for the PT. Reliability of such assessment is determined by the probabilities of not rejecting the null hypothesis when it is true, and rejecting it when it is false (the alternative hypothesis is true). It is shown that a number of chemical, metrological and statistical reasons should be taken into account for careful formulation of the hypotheses, enabling the avoidance of an erroneous assessment of the comparability. The criterion can be helpful for PT providers and laboratory accreditation bodies in analysis of PT results. 相似文献
4.
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
5.
The definition of an assigned value is usually achieved by calculating mean values from the data (with different methods)
or by designating reference laboratories. Neither method is completely satisfactory. In this paper a new method is presented
for the definition of the assigned value for spiked samples with an unknown content of the analyte in the matrix. The method
consists of two parts. The first is the estimation of the assigned values from the spiked amounts and the content in the matrix,
based on the results of reference laboratories. The other is the designation of these reference laboratories by comparing
their results with the assigned values. Because each of these parts requires the other, an iterative procedure is necessary.
As an example, the results of a proficiency test for the analysis of copper in wastewater are used to compare the calculated
values with those from other methods, e.g., the Huber estimation.
Received: 25 September 2000 Accepted: 9 December 2000 相似文献
6.
7.
Analyses of waste water are routinely performed to monitor the level of contamination. To verify the quality of such determinations
the National Institute of Chemistry, with the support of the Ministry of Environment and Spatial Planning and the Slovenian
Accreditation Agency, organizes interlaboratory comparisons. Over the last 3 years, five interlaboratory trials named "MPP-Waste
Water" were organized. Each round attracted around 50 participants, mostly from Slovenia and some from abroad, which enabled
the testing of SIST ISO methods or alternative methods. We prepared samples for determination of harmful substances that are
important for the characterization of waste water; physico-chemical parameters (pH), global parameters – chemical oxygen demand
(COD), biochemical oxygen demand (BOD5), metals (mercury, cadmium, copper, nickel, lead and chromium (VI)), nutrients (ammonia and total phosphorus), anions (chloride,
nitrite, nitrate, sulphate) and toxicity to Daphnia magna. For the analysis of each parameter we prepared two samples at two different concentration levels. The materials used in
the proficiency testing were carefully prepared and their homogeneity and stability were verified. The purpose of this scheme
was to enable participants to check their day-to-day analytical performance. The results should enable the participants to
improve the quality of their analyses.
Received: 24 October 2002 Accepted: 2 January 2003
Acknowledgments We would like to thank the Ministry of Environment and Spatial Planning and the Ministry for Education, Science and Sport for providing financial support. We would like to thank members of the Technical Committee: Mrs. Marjana Kovacˇicˇ, Dr. Katja Otrin-Debevc, Prof. Dr. Marjan Veber and Mrs. Boža Gregorc for their valuable support. Special thanks are due to Dr. Adrian Van der Veen who helped us in running the first PT.
Presented at CERMM-3, Central European Reference Materials and Measurements Conference: The function of reference materials in the measurement process, May 30–June 1, 2002, Rogaška Slatina, Slovenia
Correspondence to M. Cotman 相似文献
Received: 24 October 2002 Accepted: 2 January 2003
Acknowledgments We would like to thank the Ministry of Environment and Spatial Planning and the Ministry for Education, Science and Sport for providing financial support. We would like to thank members of the Technical Committee: Mrs. Marjana Kovacˇicˇ, Dr. Katja Otrin-Debevc, Prof. Dr. Marjan Veber and Mrs. Boža Gregorc for their valuable support. Special thanks are due to Dr. Adrian Van der Veen who helped us in running the first PT.
Presented at CERMM-3, Central European Reference Materials and Measurements Conference: The function of reference materials in the measurement process, May 30–June 1, 2002, Rogaška Slatina, Slovenia
Correspondence to M. Cotman 相似文献
8.
Petronella Mathilda van Berkel 《Accreditation and quality assurance》2001,6(4-5):210-213
Proficiency testing by laboratories, national accreditation bodies, and other third parties is becoming more and more considered
as a standard and integral part of the quality control system. Therefore, it is of utmost importance that the quality of the
provided proficiency-testing (PT) service is outstanding. If PT-schemes are set up in order to help laboratories monitor and
improve their quality, PT-schemes need not only be of high quality themselves, but the organizer also needs to be able to
demonstrate this. In The Netherlands formal accreditation of the organization of proficiency testing schemes is used as a
tool to guarantee high quality schemes and also to enable organizers to demonstrate their competence. Since 1996, the Dutch
Council for Accreditation (RvA) has used the ISO-Guide 43–1 to assess PT-organizers in The Netherlands. From January 2000,
the ISO-guide 43–1 was replaced by the ILAC G13 document for assessing organizers. Up till now, four institutes have been
accredited by the RvA for the organization of PT-schemes. 相似文献
9.
Ilya Kuselman Maria Belli Stephen L. R. Ellison Ales Fajgelj Umberto Sansone Wolfhard Wegscheider 《Accreditation and quality assurance》2007,12(11):563-567
Comparability and compatibility of proficiency testing (PT) results are discussed for schemes with a limited number of participants
(less than 20–30) based on the use of reference materials (RMs) as test items. Since PT results are a kind of measurement/analysis/test
result, their comparability is a property conditioned by traceability to measurement standards applied in the measurement
process. At the same time, metrological traceability of the certified value of the RM (sent to PT participants as test items)
is also important, since the PT results are compared with the RM certified value. The RM position in the calibration hierarchy
of measurement standards sets the degree of comparability for PT results, which can be assessed in the scheme. However, this
assessment is influenced by commutability (adequacy or match) of the matrix RM used for PT and routine samples. Compatibility
of PT results is a characteristic of the collective (group) performance of the laboratories participating in PT that can be
expressed as closeness of the distribution of the PT results to the distribution of the RM data. Achieving quality-of-measurement/analysis/test
results in the framework of the concept “tested once, accepted everywhere” requires both comparability and compatibility of
the test results. 相似文献
10.
A study of the performance of different uncertainty evaluation strategies among 163 voluntary respondents from food proficiency
schemes is presented. Strategies included use of: single-laboratory validation data, quality control data, past proficiency
testing data, reproducibility data, a measurement equation and the dispersion of replicate observations on the test material.
Most performed reasonably well, but the dispersion of replicate observations underestimated uncertainty by a factor of approximately
3. Intended compliance with accreditation requirements was associated with significantly improved uncertainty evaluation performance,
while intended compliance with the ISO “Guide to the expression of uncertainty in measurement” had no significant effect.
Substituting estimates based on the Horwitz or Horwitz–Thompson models or on PT target standard deviation for the respondents’
own estimates of uncertainty led to a marked reduction in poor zeta scores and significant improvement in dispersion of zeta
scores. 相似文献
11.
Adolf Zschunke 《Accreditation and quality assurance》1998,3(10):393-397
Global decisions made on the basis of chemical analytical results need global comparability. The concept of traceability
is important and necessary but not sufficient to achieve global comparability, especially for routine analysis in environmental
protection, health care and public safety. Sometimes comparability is only determined by the method. In this case validated
methods have to be known and recognized internationally. In addition, a minimum level of proficiency of the personnel producing
analytical results has to be guaranteed. Finally, a system of measures designed to build up trust is needed for worldwide
acceptance of analytical results. The method of self-declaration by the supplier of chemical analytical services has the advantage
of presenting specific responsibility and gaining a good reputation. Additional methods should be employed. The evaluation
of reference materials by specific quality criteria is mentioned as an example.
Received: 1 July 1998 · Accepted: 20 July 1998 相似文献
12.
Traceability of measurements still often remains a non-operational notion for end-user chemists. A practical project, sponsored by the French Ministry of Research, has been conducted to evaluate and to demonstrate possible benefits of the implementation of a metrological structure for improvement of the quality of water analyses. LNE (Laboratoire National d'Essais) was in charge of the build up of the traceability chain in a concrete case of determination of some heavy metals (cadmium and lead) in a groundwater. Pure solutions for calibration and a matrix RM have been certified by LNE and then used by 46 labs (mainly French) in a inter-laboratory study. Results have shown a measurable bias in lead analysis in the groundwater for all methods in routine use by laboratories. This project has demonstrated the interest of a metrological approach for method calibration, method validation and estimation of measurement uncertainty. 相似文献
13.
Petras Serapinas 《Accreditation and quality assurance》2007,12(11):569-574
Good correspondence between evaluations of the proficiency testing data for water measurements according to different scoring
schemes was found as a result of implementation of the measurement quality according to the target uncertainty defined in
the Drinking Water Directive. The accuracy of the evaluation is determined by the uncertainty of the assigned value, and this
uncertainty should be in correspondence with the target uncertainty. Modification of the zeta-score by the thorough application of the target uncertainty is presented. It is convenient for generalised presentation of
the proficiency testing data. The allowed bias is included as a linear term on the measured value scale, as it is treated
in uncertainty analysis. The importance of implementation of the target measurement uncertainty in other fields of the routine
measurements is indicated. 相似文献
14.
Maria Belli Stephen L. R. Ellison Ales Fajgelj Ilya Kuselman Umberto Sansone Wolfhard Wegscheider 《Accreditation and quality assurance》2007,12(8):391-398
A metrological background for the selection and use of proficiency testing (PT) schemes for a limited number N of laboratories-participants (less than 20–30) is discussed. The following basic scenarios are taken into account: (1) adequate
matrix certified reference materials (CRM) or in-house reference materials (IHRM) with traceable property values are available
for PT use as test items; (2) no appropriate matrix CRM is available, but a CRM or IHRM with traceable property values can
be applied as a spike or similar; (3) only an IHRM with limited traceability is available. The discussion also considers the
effect of a limited population of PT participants N
p on statistical assessment of the PT results for a given sample of N responses from this population. When N
p is finite and the sample fraction N/N
p is not negligible, a correction to the statistical parameters may be necessary. Scores suitable for laboratory performance
assessment in such PT schemes are compared.
Presented at the 3rd International Conference on Metrology, November 2006, Tel Aviv, Israel. 相似文献
15.
Paul De Bièvre Robert Kaarls H. Steffen Peiser Stanley D. Rasberry William P. Reed 《Accreditation and quality assurance》1996,1(1):3-13
By the definition of the mole as a base unit for amount-of-substance measures within the International System of Units (SI),
chemists can make chemical measurements in full compliance with established metrological principles. Since the mole requires
exact knowledge of the chemical entity, which is often neither available nor of practical relevance to the purpose of the
measurement, the SI units of mass or length (for volume) are unavoidable in the expression of results of many chemical measurements.
Science, technology, and trade depend upon a huge and ever increasing number and variety of chemical determinations to quantify
material composition and quality. Thus, international harmonization in the assessments of processes, procedures, and results
is highly desirable and clearly cost effective. The authors, with relevant experience and responsibilities in Europe and America,
have found some consensus in the interpretation of the metrological principles for chemical measurements, but believe open
discussion should precede wide implementation by chemical communities. In fostering this dialogue, this paper shows, for instance,
that more precise interpretation of the definitions for "traceability," "calibration," and "validation" is needed for present-day
chemical measurements. Problems that face scientists in making measurements do not all vanish just by adherence to the SI.
However, such compliance can improve communication among chemists and metrologists.
Received: 30 June 1995 Accepted: 30 June 1995 相似文献
16.
Birgitte Wuyts Dirk Bernard Nele Van Den Noortgate Johan Van De Walle Bruno Van Vlem Rita De Smet Frank De Geeter Raymond Vanholder Jean-Claude Libeer Joris Delanghe 《Accreditation and quality assurance》2004,10(1-2):15-19
When the calibration of a routine measurement procedure is traced back to metrological higher order, a significant discrepancy can occur between the analytical conditions of the routine measurement and the analytical conditions that were used in the clinical studies upon which the decision-making criteria are based. This can lead to serious interpretation errors with possible dramatic consequences for patients. The calibration of the creatinine Jaffé method is an excellent example of the importance of medical traceability. The compensated Jaffé method correlated accurately with the reference method and the compensated Jaffé creatinine clearance (CrCl), Cockroft and Gault and MDRD with the 51Cr EDTA clearance. The Schwartz estimate based upon the compensated Jaffé and enzymatic method overestimated, while uncompensated Jaffé slightly underestimated glomerular filtration rate (GFR). The situation in children is complex since serum creatinine concentrations are much lower in infants, rendering tubular secretion relatively more important. Low-molecular weight proteins have been suggested to replace serum creatinine as a marker for GFR. -trace protein, cystatin C, and 2-microglobulin showed good correlation with GFR. However, care should be taken in patients presenting with some malignant tumors, since significant increases of cystatin C in patients with metastatic melanoma or colorectal cancer has been reported.Presented at the 9th Conference on Quality in the Spotlight, 18-19 March 2004, Antwerp, Belgium 相似文献
17.
O. Bercaru M. Ricci F. Ulberth C. Brunori R. Morabito I. Ipolyi A. Sahuquillo E. Rosenberg 《Trends in analytical chemistry : TRAC》2009,28(9):1073-1081
In accordance with Article 8 of the European Union (EU) Water Framework Directive (WFD), EU Member States are required to establish monitoring programs for the quality of the surface water and the groundwater within each river-basin district. As such data are the basis for regulatory decisions and measures required to achieve WFD environmental objectives, appropriate analytical quality-assurance and quality-control tools have to be implemented by the monitoring laboratories. In this respect, reference materials (RMs) play a key role. Within the framework of the SWIFT-WFD project (Screening methods for Water data InFormation in support of the WFD), several approaches to the preparation of matrix RMs for the analysis of polycyclic aromatic hydrocarbons and pesticides in water have been used in wide-scale proficiency-testing (PT) schemes. We present the different strategies employed in preparing water-matrix RMs for organic analytes. By reviewing the results from the SWIFT-WFD PT schemes, we reflect on the applicability and the suitability of the different approaches. 相似文献
18.
Ilya Kuselman 《Accreditation and quality assurance》2006,10(12):659-663
A nonparametric sign test is implemented for assessment of comparability of proficiency testing (PT) results when their distribution differs from the normal or other known distribution. It allows testing the null hypothesis about insignificance of the bias of median of results obtained in PT from the traceable certified value of the reference material used in PT as test items, i.e., the hypothesis stating that comparability of the PT results is successful. Probability of type I error of rejecting the null hypothesis when it is true, and probability of type II error of it not rejecting when it is false (the alternative hypothesis about unsuccessful comparability is true) are considered. The test can be helpful for PT providers and laboratory accreditation bodies in analysis of PT results when the comparability criterion developed for a normal results distribution (Accred. Qual. Assur. 10:466–470) is not applicable. 相似文献
19.
20.
Adriaan M. H. van der Veen 《Accreditation and quality assurance》2001,6(4-5):160-163
The evaluation of measurement uncertainty, and that of uncertainty statements of participating laboratories will be a challenge
to be met in the coming years. The publication of ISO 17025 has led to the situation that testing laboratories should, to
a certain extent, meet the same requirements regarding measurement uncertainty and traceability. As a consequence, proficiency
test organizers should deal with the issues measurement uncertainty and traceability as well. Two common statistical models
used in proficiency testing are revisited to explore the options to include the evaluation of the measurement uncertainty
of the PTRV (proficiency test reference value). Furthermore, the use of this PTRV and its uncertainty estimate for assessing
the uncertainty statements of the participants for the two models will be discussed. It is concluded that in analogy to Key
Comparisons it is feasible to implement proficiency tests in such a way, that the new requirements can be met.
Received: 29 September 2000 Accepted: 3 December 2000 相似文献