共查询到20条相似文献,搜索用时 810 毫秒
1.
Martina Bednarova Yetunde Aregbe Caroline Harper Philip D. P. Taylor 《Accreditation and quality assurance》2006,10(11):617-626
The aim of International Evaluation Programme (IMEP) is to present objectively the quality of chemical measurements. Participants in IMEP compare their reported measurement results with independent external certified reference values with demonstrated traceability and uncertainty, as evaluated according to international guidelines. Three major interlaboratory comparisons (ILCs), IMEP-6, IMEP-9 and IMEP-12, on trace elements in water were carried out from 1994 to 2000. Participants' results for Cd, Fe and Pb concentrations from these three different IMEP water ILCs were compared by means of suitable performance indicators. The performance evaluation criteria were set according to the requirements stated in the Council Directive 98/83/EC of 3 November 1998 on the quality of water intended for human consumption. Two different performance indicators were selected for evaluation of the individual participants' results: the commonly used z-score and the not so well-known E
n
number. The group performance indicator is based on the variation of z-scores. To assess the individual measurement performance, not only the deviation of the reported measurement values from the certified reference value, but also criteria for maximum and minimum acceptable uncertainties were taken into account. The participants' performance is also reviewed by means of using a simple graphical tool, called “Naji-plots”. 相似文献
2.
The aim of IMEP is to present objectively the quality of chemical measurements. Participants in IMEP compare their reported measurement results with independent external certified reference values with demonstrated traceability and uncertainty, as evaluated according to international guidelines. IMEP-19 focused on measurements of trace elements in rice aiming to support the Commission Regulation (EC) No. 466/2001 on maximum levels for certain contaminants in foodstuff. Measurement results for the elements Cd, Cu, Pb and Zn were reported by 267 field laboratories involved in food analysis from 43 countries. Performance criteria for the evaluation of the reported measurement results in IMEP-19 are suggested. The chosen performance indicators not only take into account the deviation of the reported measurement value from the certified reference value, but also set criteria for maximum and minimum acceptable uncertainty. The IMEP-19 participants' performance is reviewed by means of using new simple graphical tools, called "Naji plots". 相似文献
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介绍电导检测器离子色谱检定方法。采用氯离子标准物质,使用泵流量设定值误差、流量稳定性、基线噪声、基线漂移、最小检测浓度、线性相关性、整机性能定性定量重复性等参数对离子色谱仪进行检定。同时用5 μg/mL氯离子为检测离子,结合JJF 1059.1–2012 《测量不确定度评定与表示》对整机性能不确定度来源进行考察。结果表明:在置信区间为95%时(包含因子k=2),氯离子的质量浓度为(4.94±0.35)μg/mL。经不确定度分析,标准工作曲线拟合引入的不确定度最大,其次是样品的重复随机测试过程。 相似文献
5.
Manuel Alvarez-Prieto Juan Jiménez-Chacón Álvaro Montero-Curbelo 《Accreditation and quality assurance》2009,14(11):623-634
Along the years, several approaches for measurement uncertainty estimation have been suggested. Emphasis has been put on the
general metrological interpretation of measurement uncertainty, but not on its different meanings when it is associated to
given conditions of measurement where analytical work is performed and errors are originated. Three different definitions
for uncertainty are proposed for reproducibility and intermediate precision conditions of measurement. These definitions inherit
features from the VIM 3 definition of measurement uncertainty. It is argued that if a high performance laboratory keeps errors
under control with proper validation and quality assurance programs, measurement uncertainty from intermediate precision condition
of measurement is justified as a suitable estimation of its capability to attribute values to a measurand. Alternatively,
a laboratory that does not keep errors under control should use uncertainty from reproducibility condition of measurement
as the cost of its imperfections. Selection of information sources for measurement uncertainty estimation should be in harmony
with its metrological meaning. 相似文献
6.
原子荧光光谱法测定方便米饭中砷的测量不确定度评定 总被引:2,自引:0,他引:2
蔡秋 《理化检验(化学分册)》2007,43(2):122-126
介绍了原子荧光光谱法测定方便米饭中砷的测量不确定度评定方法,该法根据最小二乘法原理计算校准曲线的标准不确定度,并充分分析和识别分析过程中的不确定度来源,较为全面地评定了测量不确定度,该法对原子吸收光谱法、电感耦合等离子发射光谱法和原子荧光光谱法等测定结果的不确定度评定具有参考作用。 相似文献
7.
Assessment and expression of analytical quality have become novel spotlights in medical laboratories since accreditation began in the early 1990s, in Europe. Evaluation of uncertainty of measurement by definition was launched in Finland when the Finnish Accreditation Service (FINAS) accredited the first medical laboratories in the mid 1990s. In spite of all the analytical and statistical knowledge which has been available in medical laboratories for years, evaluation of total uncertainty of measurement has not yet caught on. The concept is still unfamiliar to experts and, indeed, little guidance has been available. National and international activities, with good results, can be shown when the educational aspect is considered. The Guide to the Expression of Uncertainty in Measurement (GUM) remains the main document for uncertainty evaluation. Uncertainty of measurement together with target value of uncertainty can be used as a good measure for analytical quality in large or smaller laboratories over time, because it is a quantitative indication and the evaluation is easy to repeat as running practical tools are available.Presented at the 8th Conference on Quality in the Spotlight, 17–18 March 2003, Antwerp, Belgium 相似文献
8.
The performance of all four GOLD scoring functions has been evaluated for pose prediction and virtual screening under the standardized conditions of the comparative docking and scoring experiment reported in this Edition. Excellent pose prediction and good virtual screening performance was demonstrated using unmodified protein models and default parameter settings. The best performing scoring function for both pose prediction and virtual screening was demonstrated to be the recently introduced scoring function ChemPLP. We conclude that existing docking programs already perform close to optimally in the cognate pose prediction experiments currently carried out and that more stringent pose prediction tests should be used in the future. These should employ cross-docking sets. Evaluation of virtual screening performance remains problematic and much remains to be done to improve the usefulness of publically available active and decoy sets for virtual screening. Finally we suggest that, for certain target/scoring function combinations, good enrichment may sometimes be a consequence of 2D property recognition rather than a modelling of the correct 3D interactions. 相似文献
9.
A statistical analysis of multi-point calibration procedure for practical measurement of pH under laboratory conditions is
given. The procedure is shown to provide the necessary elements for simple assignment of an uncertainty to a pH measurement
– an essential element of quality control. Performance of ordinary least squares regression for prediction of confidence limits
is compared to orthogonal regression, inverse regression and Monte Carlo simulations. In case of pH measurement by multi-point
calibration procedure, methods considering uncertainties in both axes are found to be statistically more satisfactory than
ordinary least squares regression. By analysis of 50 pH calibration data, randomly selected from 250 5-point glass electrode
calibrations, it is found that the practical differences, however, are of minor importance. The significance of uncertainty
in pH is demonstrated for an example from metal ion speciation in aqueous solution.
Received September 20, 1999. Revision April 19, 2000. 相似文献
10.
The expression of results with an uncertainty through the "bottom-up" approach, involving the estimation and combination of all the sources of uncertainty, represents a challenge when the analytical method includes mass transfer steps (MTS). These steps (e.g. extraction, evaporation, digestion, etc.) with inherently different from 100% recoveries lack models capable of describing their precision and efficiency. Recently, a new methodology was published aimed at the estimation of the performance of these critical steps. Comparison of the experimental dispersion from the replicated analysis of spiked samples with the combination of the uncertainty associated with gravimetric, volumetric and instrumental quantification steps (described by well established models) allows the estimation of the MTS uncertainty. Evaluation of the behaviour of the MTS within the analytical range supports the use of developed estimations over a wide concentration range. This methodology was applied, with success, to the determination of pesticide residues in melon in one particular proficiency test organised by the Food Analysis Performance Assessment Scheme (FAPAS) between November 2000 and February 2001. 相似文献
11.
Rozet E Rudaz S Marini RD Ziémons E Boulanger B Hubert P 《Analytica chimica acta》2011,702(2):160-171
Evaluation of analytical results reliability is of core importance as crucial decisions are taken with them. From the various methodologies to evaluate the fitness of purpose of analytical methods, overall measurement uncertainty estimation is more and more applied. Overall measurement uncertainty allows to combine simultaneously the remaining systematic influences to the random sources of uncertainty and allows assessing the reliability of results generated by analytical methods. However there are various interpretations on how to estimate overall measurement uncertainty, and thus various models for estimating it. Each model together with its assumptions has great impacts on the risks to abusively declare that analytical methods are suitable for their intended purpose. This review paper aims at (i) summarizing the various models used to estimate overall measurement uncertainty, (ii) provide their pros and cons, (iii) review the main areas of application and (iv) as a conclusion provide some recommendations when evaluating overall measurement uncertainty. 相似文献
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Frequently, the ultimate goal of an analytical measurement is to assess compliance in respect to a specification limit. So,
the necessary requirement is to make a correct decision on the grounds of the measurement result. It is suggested a practical
methodology to attain fitness for purpose results when specification limits are established for compliance assessment. It
is based on a comparison between fitness for purpose uncertainty functions that define a high probability of conclusive correct
decisions and a characteristic uncertainty function which describes the performance of the analytical system along concentration
in a given condition of measurement. To attain fitness for purpose results, different replication programs are applied. Determinations
of Zn, Mn and Cd in potable water are discussed as case studies. They represent different cases concerning relative position
of detection and specification limits. A definition of fitness for purpose when specification limits are relevant is given.
Quality of analytical results and analytical procedures should be associated with the concept of fitness for purpose. 相似文献
14.
Siu Kay Wong 《Accreditation and quality assurance》2007,12(2):59-66
Recently, ISO issued a new document on statistical methods for use in proficiency-testing schemes. The document presented
a number of new performance statistics that involve the use of measurement uncertainties of the participants’ results and/or
the assigned values for the performance evaluation. Making use of the Monte Carlo simulation technique, this paper attempts
to compare selected performance statistics of different approaches. In addition, the simulation programme was extended to
study the effect of multi-modality in participants’ results on the performance evaluation when different performance statistics
were applied. 相似文献
15.
Analysis of interlaboratory performance in the determination of total selenium in water 总被引:1,自引:0,他引:1
This study explored the performance of experienced laboratories in the analysis for total selenium in water by a variety of analytical methods. The goal of the study was to examine intra- and interlaboratory variability. Replicates (n = 7) of 7 sample types that included a reference material of known Se concentration, natural waters, and treated wastewaters were submitted to 7 laboratories with prequalified Se analytical experience. Results of the study indicated wide ranges in minimum and maximum results, distinct differences in laboratory precision, and routine reporting of numerical results below statistical limits of quantitation. Hydride generation as a sample introduction technique demonstrated superior performance. In general, the study supports a caution advisory about using low-level Se data, especially results lower than about 10 micrograms Se/L, without quantitating the statistical uncertainty of the data. Because this study used data from samples that were submitted in bulk to participating laboratories prequalified for Se analytical expertise and experience, it can be considered a best-case demonstration of performance. 相似文献
16.
Forster LI 《Journal of AOAC International》2003,86(5):1089-1094
Testing laboratories wishing to comply with the requirements of ISO/IEC 17025:1999 need to estimate uncertainty of measurement for their quantitative methods. Many microbiological laboratories have had procedures available for monitoring variability in duplicate results generated by laboratory analysts for some time. These procedures, however, do not necessarily include all possible contributions to uncertainty in the calculations. Procedures for estimating microbiological method uncertainty, based on the Poisson distribution, have been published but, at times, the procedures can either underestimate uncertainty or require laboratories to undertake considerable experimental studies and more complex statistical calculations. This paper proposes procedures for estimating uncertainty of measurement in microbiology, whereby routine laboratory quality control data can be analyzed with simple statistical equations. The approaches used in these procedures are also applied to published data and examples, demonstrating that essentially equivalent results can be obtained with these procedures. 相似文献
17.
雷宏田 《中国无机分析化学》2012,2(1)
讨论了采用电感耦合等离子体发射光谱法测定铜合金中锆量分析结果不确定度产生的原因。建立了数学模型,对测量重复性,标准溶液,标准曲线变动性,试液体积,试样称量,数字修约等引起的不确定分量进行评定,计算了合成标准不确定度和扩展不确定度,并给出铜合金中锆量测定结果的报告。评定结果表明:测量重复性,标准曲线线性回归引起的不确定度对总不确定度影响最大。所以,在测定中应进行多次平行测定,特别注意标准曲线的校正和绘制校准曲线所用标准样品的选择。 相似文献
18.
气相色谱仪检测器的灵敏度和检测限测量结果不确定度的评定 总被引:3,自引:0,他引:3
依据JJF1059-1999《测量不确定度评定与表示》评定了气相色谱仪检测器的主要技术指标灵敏度和检测限测量结果的不确定度。分析了各不确定度分量,建立了评定灵敏度、检测限测量结果不确定度的数学模型,并计算了其测量结果的扩展不确定度。 相似文献
19.
I. Papadakis P. D. P. Taylor P. D. Bièvre 《Analytical and bioanalytical chemistry》1997,357(8):1020-1023
The certification measurement for the cadmium concentration in the samples as performed by Isotope Dilution (ID) using Inductively
Coupled Plasma Mass Spectrometry (ICP-MS) is described in framework of the International Measurement Evaluation Programme
(IMEP). By using a primary method of measurement (ID), making up a full uncertainty budget and using a sensitive technique
(ICP-MS), reference values traceable to SI can be obtained for this material.
The uncertainty budget is performed in accordance with the ISO and EURACHEM guides on uncertainty. A comparison is made with
certification results of other experienced laboratories also using primary methods where possible.
Received: 8 July 1996/Revised 26 August 1996/Accepted: 1 September 1996 相似文献
20.
Susanna Murtas Andrea Gaggioli Christina von Hunolstein 《Accreditation and quality assurance》2012,17(2):177-182
The measurement uncertainty in quantifying polysaccharides in glycoconjugate vaccines was estimated in order to ascertain
compliance of these products in the batch release procedure of an Official Medicines Control Laboratory. A single-laboratory
validation approach of an internal analytical procedure to quantify the total saccharide by the way of the sialic acid (N-Acetylneuraminic acid) concentration in a meningococcal glycoconjugate vaccine by High Performance Anion Exchange Chromatography
coupled with Pulsed Amperometric Detection is reported. Uncertainty components from precision, bias and other sources were
evaluated. It turned out that uncertainty is dominated by the precision contribution, while bias was mainly due to the non-recovery
from hydrolysis. As a consequence, a correction factor was considered. At a confidence level of approximately 95%, the expanded
uncertainty of the total polysaccharide concentration in a vaccine, when measured using the internal method, was found to
be 11.5%. 相似文献