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1.
Brian Belanger 《Accreditation and quality assurance》2001,6(3):100-102
During the last quarter of the twentieth century, The United States National Bureau of Standards (NBS), later the National
Institute of Standards and Technology (NIST), introduced a measurement quality control concept called ”measurement assurance,”
and developed measurement assurance programs, or MAPs, for high-level calibration processes. The measurement assurance approach
has, over time, become increasingly popular in the metrology community, and in recent years has become well accepted both
inside and, to some extent, outside the United States as a rigorous way to ensure the quality of calibrations. The concept
has also found application in defining traceability to national standards. This paper traces the history of the measurement
assurance concept.
Received: 23 October 2000 Accepted: 2 November 2000 相似文献
2.
T. Drglin 《Accreditation and quality assurance》2003,8(3-4):130-133
A validation procedure based on the ISO/IEC 17025 standard was used to demonstrate the long-term stability of a calibration
process and to assess the measurement uncertainty of a standard test method for optical emission vacuum spectrometric analysis
of carbon and low-alloy steel (ASTM E 415–99a). The validation was used to provide documented evidence that the selected method
fulfils the requirements and that the method is ”fit for purpose”. A test for drift was applied to determine statistically
whether the analytical results vary systematically with time. The accuracy and traceability of the optimised method were tested
by an analysis of closely matched matrix certified reference materials (CRMs). The measurement uncertainty estimations took
account of the precision study, the bias and its uncertainty, and the qualification of uncertainties not considered in the
overall performance studies.
Received: 2 November 2002 Accepted: 2 January 2003
Acknowledgement The author expresses gratitude to Dr. Aleš Fajgelj for helpful discussions during the 3rd Central European Conference on Reference Materials and Measurements.
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 T. Drglin 相似文献
3.
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
4.
Marc Priel 《Accreditation and quality assurance》2009,14(5):235-241
Since the advent of the Guide to the expression of Uncertainty in Measurement (GUM) in 1995 laying the principles of uncertainty
evaluation numerous projects have been carried out to develop alternative practical methods that are easier to implement namely
when it is impossible to model the measurement process for technical or economical aspects. In this paper, the author presents
the recent evolution of measurement uncertainty evaluation methods. The evaluation of measurement uncertainty can be presented
according to two axes based on intralaboratory and interlaboratory approaches. The intralaboratory approach includes “the
modelling approach” (application of the procedure described in section 8 of the GUM, known as GUM uncertainty framework) and
“the single laboratory validation approach”. The interlaboratory approaches are based on collaborative studies and they are
respectively named “interlaboratory validation approach” and “proficiency testing approach”. 相似文献
5.
Sébastien Sannac Paola Fisicaro Guillaume Labarraque Florence Pannier Martine Potin-Gautier 《Accreditation and quality assurance》2009,14(5):263-267
The development of an analytical procedure for speciation analysis of methylmercury in fish products is presented. The method
is based on high-performance liquid chromatography hyphenated to inductively coupled plasma-mass spectrometry. The metrological
approach is stressed out in this paper, in order to provide reliable and comparable results. A complete uncertainty budget
has been evaluated and the method has been validated by the use of a certified reference material. Moreover, the detection
could rely on the isotope dilution mass spectrometry, a powerful strategy capable of highly accurate results traceable to
the “Système International d’Unités” and recognised by the “Comité Consultatif pour la Quantité de Matière” as a primary method
of measurement.
Presented at MEFNM 2008, September 2008, Budapest, Hungary. 相似文献
6.
Quality assurance in analytical measurement 总被引:2,自引:0,他引:2
The peculiarities of analytical measurement require to check characteristics of the error (its components) of the obtained
analysis results to assure the quality of the measurements. This article deals with the various quality assurance procedures
and algorithms which are used to check the quality indices, i.e. the accuracy, reproducibility, certainty and repeatability
of analytical measurements: These procedures include: laboratory rapid control; Intra-laboratory statistical control (statistical
selection control by alternative attribute, statistical selection control by quantity method of periodic check of the analysis
procedure for conformity to the specified requirements) and external control (inter-laboratory control checks, inter-laboratory
comparison tests, and intra-laboratory control algorithms carried out by the appropriate supervisory body.) in the separately
taken laboratory. The respective algorithms, control plans and control requirements, specified according to the different
control aims and assurance tasks, enable the quality and certianty of analytical information obtained in laboratories in Russia
to be assured.
Received: 9 November 1998 / Accepted: 24 November 1998 相似文献
7.
R. Dybkaer Ulf Örnemark Adam Uldall Wolfgang Richter 《Accreditation and quality assurance》1999,4(8):349-351
In a recent Letter to the Editor, Dr. B. Neidhart questioned the need to make clinical chemical measurement results traceable to international standards and
to incorporate the principles of analytical quality assurance into clinical chemistry. An analysis of the arguments presented
shows that modern laboratory medicine has to deliver accurate results, which are comparable over space and time, in order
to improve the accuracy of diagnostic tools and minimize cost. The means to achieve accuracy and comparability are metrological
traceability and quality assurance as supported by many national and international initiatives. 相似文献
8.
Ricardo J. N. Bettencourt da Silva Maria Filomena G. F. C. Camões 《Accreditation and quality assurance》2010,15(12):691-704
The dispersion of results from proficiency tests for the analysis of pesticide residues in foodstuffs suggests that improvements
in the compatibility of measurement results are needed. Currently observed divergences can make the evaluation conclusion
on foodstuffs compliance with certain legislation dependent on the consulted laboratory. This work discusses the origin and
impact of this lack of compatibility, following the metrological concepts presented at the latest version of the “International
Vocabulary of Metrology” (VIM3), thus allowing for a clear diagnostic of the problem. The reporting of results from different
measurement methods uncorrected for the observed analyte recovery makes them traceable to different “operationally defined
measurement procedures” (VIM3) and, therefore, not comparable. When results from different measurement methods are reported
corrected for analyte recovery, R, and R is different for spiked and incurred residues, measurement results may be not compatible if this effect is not considered
on the uncertainty budget. This discussion is illustrated with metrological models for any possible combination of “measurement
performance” and “maximum residue level”. These models are complemented with experimental data of the analysis of pesticide
residues in a sample of ginseng powder from a proficiency test. The adopted experimental design allowed the identification
of additional threats to metrological compatibility in this field. Solutions to the faced problem are discussed for practicability
and impact on regulatory issues. The use of a universal “reference measurement procedure” proves to be the most feasible way
of ensuring comparability of measurements in this field. 相似文献
9.
In the EURACHEM/CITAC draft ”Quantifying uncertainty in analytical measurement” estimations of measurement uncertainty in
analytical results for linear calibration are given. In this work these estimations are compared, i.e. the uncertainty deduced
from repeated observations of the sample vs. the uncertainty deduced from the standard residual deviation of the regression.
As a result of this study it is shown that an uncertainty estimation based on repeated observations can give more realistic
values if the condition of variance homogeneity is not correctly fulfilled in the calibration range. The complete calculation
of measurement uncertainty including assessment of trueness is represented by an example concerning the determination of zinc
in sediment samples using ICP-atomic emission spectrometry.
Received: 9 February 2002 Accepted: 17 April 2002 相似文献
10.
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
11.
Mayer Brezis 《Accreditation and quality assurance》2011,16(12):599-602
The illusion of accuracy and precision in testing is often associated with overconfident safety checks before catastrophes:
National Aeronautics and Space Administration (NASA) “no safety-of-flight issues,” Deepwater Horizon site in Gulf Mexico reported
as “industry model for safety” a year before its explosion, and Fukushima nuclear plant safety test found “satisfactory” at
seismic magnitude viewed highest possible. In health care, testing overuse and misuse play significant roles in overconfidence
and mistakes. Gaps between systems are most susceptible to errors, such as in miscommunications between the laboratory and
the clinic. A safety culture is characterized by ability to communicate, anticipation of misunderstanding and resilient learning
from failures. The discussion will show how messages from the laboratory may reduce the false sense of certainty from a test
result; how results of tests are meaningless without pre-test estimates; how multiplicity of routine tests increases chances
of false positivity; and how reporting measurement limitations can educate all users, including laboratory technicians, clinicians
and patients, about the importance of quality assurance and about the pervasive nature of uncertainty beyond analytical performance.
In conclusion, an illusion of accuracy and precision in testing evokes among clinicians a false sense of certainty leading
to overuse and misuse of tests. Messages from the laboratory may reduce overconfidence from test results and lead to safer
use of testing. 相似文献
12.
S. Küppers 《Accreditation and quality assurance》1997,2(1):30-35
Any analytical data is used to provide information about a sample. The "possible error" of the measurement can be of extreme
importance in order to have complete information. The measurement uncertainty concept is a way to achieve quantitative information
about this "possible error" using an estimation procedure. On the basis of the analytical result, the chemist makes a decision
on the next step of the development process. If the uncertainty is unknown, the information is not complete; therefore this
decision might be impossible. The major problem for the in-process control (IPC) procedure is that not only the repeatability
but also the intermediate precision (which expresses the variations within laboratories related to different days, different
analysts, different equipment, etc.) has to be good enough to make a decision. Unfortunately, the statistical information
achieved from one single analytical run only gives information about the repeatability. This paper shows that the estimation
of the measurement uncertainty for IPC is a way to solve the problem and gives the necessary information about the quality
of the procedure. An example demonstrates that an estimate of uncertainty based on the standard deviations of an analytical
method gives a value similar to one based on the standard deviations obtained from a control chart. Therefore, the estimation
is both a very useful and also a very cost-effective tool. Though measurement uncertainty cannot replace validation in general,
it is a viable alternative to validation for all methods that will never be used routinely.
Received: 24 May 1996 Accepted: 10 August 1996 相似文献
13.
Historically, due to the size and nature of the instrumentation, highly skilled laboratory professionals performed clinical
testing in centralized laboratories. Today’s clinicians demand realtime test data at the point of care. This has led to a
new generation of compact, portable instruments permitting ”laboratory” testing to be performed at or near the patient’s bedside
by nonlaboratory workers who are unfamiliar with testing practices. Poorly controlled testing processes leading to poor quality
test results are an insidious problem facing point of care testing today. Manufacturers are addressing this issue through
instrument design. Providers of clinical test results, regardless of location, working with manufacturers and regulators must
create and manage complete test systems that eliminate or minimize sources of error. The National Committee for Clinical Laboratory
Standards (NCCLS) in its EP18 guideline, ”Quality management for unit-use testing,” has developed a quality management system
approach specifically for test devices used for point of care testing (POCT). Simply stated, EP18 utilizes a ”sources of error”
matrix to identify and address potential errors that can impact the test result. The key is the quality systems approach where
all stakeholders – professionals, manufacturers and regulators – collaboratively seek ways to manage errors and ensure quality. We illustrate the use of one quality systems approach, EP18, as a means to advance the quality of test results at point of
care.
Received: 26 June, 2002 Accepted: 17 July 2002
Presented at the European Conference on Quality in the Spotlight in Medical Laboratories, 7–9 October 2001, Antwerp, Belgium
Abbreviations NCCLS National Committee for Clinical Laboratory Standards (formerly) · POCT point of care testing · QC quality control ·
HACCP hazard analysis critical control points · CLIA clinical laboratory improvement amendments (of 1988)
Correspondence to S. S. Ehrmeyer 相似文献
14.
Reference materials have been applied widely to ensure the traceability, comparability and reliability of measurement results.
To achieve this purpose, the quality of reference materials (RMs) themselves is surely an important aspect to be pay attention
to. A quality evaluation system of RMs has been established through the project “The National Sharing Platform of Reference
Materials” in China to give a reliable assessment on the quality of RMs from various sources including the accuracy and comparability
of their property values, which is very useful to promote the appropriate selecting and using of RMs in China. Through the
application of National Metrology Institute calibration and measurement capabilities on the basis of the international mutual
recognition arrangement, it can also provide a powerful supplement to the current activities such as the accreditation of
RM producers in the construction of a global harmonized quality control and assurance system of RMs. 相似文献
15.
Stefania?Gaudino Chiara?Galas Maria?Belli Sabrina?Barbizzi Paolo?de?Zorzi Radojko?Ja?imovi? Zvonka?Jeran Alessandra?Pati Umberto?Sansone
The measurement of trace-element concentration in soil, sediment and waste, is generally a combination of a digestion procedure
for dissolution of elements and a subsequent measurement of the dissolved elements. “Partial” and “total” digestion methods
can be used in environmental monitoring activities. To compare measurement results obtained by different methods, it is crucial
to determine and to maintain control of the bias of the results obtained by these methods. In this paper, ICP-MS results obtained
after matrix digestion with modified aqua regia (HCl+HNO3+H2O2) method and two “total” digestion methods (microwave aqua regia+HF and HNO3+HF) are compared with those obtained by instrumental neutron activation analysis, a non-destructive analytical method for
the determination of the total mass concentrations of inorganic components in environmental matrices. The comparison was carried
out on eight agricultural soil samples collected in one test area and measured by k0-INAA and ICP-MS to determine As, Co, Cr, Sb and Zn mass concentration. The bias of results for As, Cd, Co, Cr, Cu, Ni, Pb,
Sb and Zn of the three digestion methods were assessed using selected measurement standards. This paper highlights that the
digestion procedure is an integral part of the measurement and can affect the measurement result in environmental analysis. 相似文献
16.
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
17.
David Lee Duewer 《Accreditation and quality assurance》2008,13(4-5):193-216
While estimation of measurement uncertainty (MU) is increasingly acknowledged as an essential component of the chemical measurement
process, there is little agreement on how best to use even nominally well-estimated MU. There are philosophical and practical
issues involved in defining what is “best” for a given data set; however, there is remarkably little guidance on how well
different MU-using estimators perform with imperfect data. This report characterizes the bias, efficiency, and robustness
properties for several commonly used or recently proposed estimators of true location, μ, using “Monte Carlo” (MC) evaluation of “measurement” data sets drawn from well-defined distributions. These synthetic models
address a number of issues pertinent to interlaboratory comparisons studies. While the MC results do not provide specific
guidance on “which estimator is best” for any given set of real data, they do provide broad insight into the expected relative
performance within broadly defined scenarios. Perhaps the broadest and most emphatic guidance from the present study is that
(1) well-estimated measurement uncertainties can be used to improve the reliability of location determination and (2) some
approaches to using measurement uncertainties are better than others. The traditional inverse squared uncertainty-weighted
estimators perform well only in the absence of unrepresentative values (value outliers) or underestimated uncertainties (uncertainty
outliers); even modest contamination by such outliers may result in relatively inaccurate estimates. In contrast, some inverse
total variance-weighted-estimators and probability density function area-based estimators perform well for all scenarios evaluated,
including underestimated uncertainties, extreme value outliers, and asymmetric contamination. 相似文献
18.
The potential of a headspace device coupled to multi-capillary column-ion mobility spectrometry has been studied as a screening
system to differentiate virgin olive oils (“lampante,” “virgin,” and “extra virgin” olive oil). The last two types are virgin olive oil samples of very similar characteristics,
which were very difficult to distinguish with the existing analytical method. The procedure involves the direct introduction
of the virgin olive oil sample into a vial, headspace generation, and automatic injection of the volatiles into a gas chromatograph-ion
mobility spectrometer. The data obtained after the analysis by duplicate of 98 samples of three different categories of virgin
olive oils, were preprocessed and submitted to a detailed chemometric treatment to classify the virgin olive oil samples according
to their sensory quality. The same virgin olive oil samples were also analyzed by an expert’s panel to establish their category
and use these data as reference values to check the potential of this new screening system. This comparison confirms the potential
of the results presented here. The model was able to classify 97% of virgin olive oil samples in their corresponding group.
Finally, the chemometric method was validated obtaining a percentage of prediction of 87%. These results provide promising
perspectives for the use of ion mobility spectrometry to differentiate virgin olive oil samples according to their quality
instead of using the classical analytical procedure. 相似文献
19.
Michael Gluschke 《Accreditation and quality assurance》2008,13(2):101-107
This paper presents the assessment of a collaborative trial in sampling in the Baltic Sea in the framework of quality assurance
in the German marine monitoring programme for the North Sea and the Baltic Sea. The objective of investigations was to determine
the influence of sampling on analytical results for selected monitoring parameters and to harmonize the procedure for sampling
of sea water to a large extent. In these studies the staff of three vessels took replicate sea water samples, 1 m below the
surface and below the halocline, at two monitoring stations. Mass concentration mean values for different nutrient parameters
were obtained from each sample, all in one laboratory. Data produced from the hierarchical design were treated with robust
analysis of variance (ANOVA) to generate uncertainty estimates, as standard uncertainties (“u” expressed as standard deviation), for geochemical variation (s
geochem), primary sampling (s
sampling), and chemical analysis (s
analysis). Geochemical variation dominated the total variance in all cases. Sampling and analytical uncertainties contributed together
up to 15% of the total variance and had a relative measurement uncertainty (u%) of less than 2% for all the parameters investigated. Thus for this study the sampling protocol and the analytical method
could be regarded as fit-for-purpose.
M. Gluschke was formerly affiliated to the Federal Environmental Agency, P.O. Box 33 00 22, 14191 Berlin, Germany. 相似文献
20.
S. Duta 《Accreditation and quality assurance》2000,5(8):339-345
The objective of quality assurance programme for spectrochemical measurements is to reduce the measurement errors to accepted
limits. Reference materials are being widely used as measurement standards in the fields of industrial production, environmental
protection and clinical chemistry, and are playing an important role in ensuring the quality of measurement results. This
paper presents some aspects, practices and examples of the activity of the Reference Materials Laboratory of the National
Institute of Metrology, Bucharest, in the field of spectrochemical measurements. An attempt to describe the role and use of
reliable certified reference materials to ensure the quality of spectrochemical measurements is presented. A short review
of the locally available certified reference materials used in spectrochemical measurements is given. The use of reference
materials data in estimating the measurement uncertainty is discussed. An interlaboratory comparison, recently organized in
Romania, is also presented as a useful response to the need for quality assurance of spectrochemical results.
Received: 20 March 1999 / Accepted: 25 February 2000 相似文献