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121.
Three round robins, involving 22 laboratories from eight countries, were conducted at six month intervals. Each of the participating laboratories analysed four samples of NIES-13 in three subsequent round robins during July 2000–October 2001. The objective of the current study was to determine accuracy and precision among participants for the analysis of total mercury. Both accuracy and precision for total mercury determinations in powder hair samples were good. The median within-laboratory (within-run) CVs ranged from 3.1 to 3.9% for four CRM samples. Most laboratories showed a proportional bias relative to the consensus mean of up to 16%. Two laboratories reported results that, on average, were almost 30% higher than the consensus mean value. Significant among-laboratory imprecision was found in the present study. Improvements are needed to reduce the analytical imprecision in a few laboratories, and attention must be focused on calibration issues and methodology-related problems.
相似文献
Udai S. GillEmail: Phone: +1-613-957-8549Fax: +1-613-946-2340 |
122.
An asymptotic exponential convergence rate of ordinal comparison from large deviations theory is well known for selecting the true best solution from the candidate solutions sample means. This note supplements the theories developed by Dai within the framework of ergodic Markov reward processes for -ordinal comparison of policies, establishing an asymptotic exponential convergence rate for the infinite-horizon average criterion. 相似文献
123.
Jan W. Owsiński 《Annals of Operations Research》1994,51(5):217-240
This paper presents a model for analysis and a practical method of management of a session meant at attainment of consensus regarding preferences over a set of multi-aspect options, these preferences being expressed through pairwise comparisons or orderings. The model and the method accept and process valued or fuzzy preferences, while preserving an entirely crisp procedure throughout the approach. The aggregation method presented previously in Owsiski and Zadrony [17, 18] is referred to and expanded for the case of clusterwise preference aggregation and consensus measurement. The framework of the clustering approach of Owsiski [19] is applied, allowing for a natural definition of consensus. 相似文献
124.
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
125.
Multivariate self-modeling curve resolution is applied to the quantitation of coeluted organophosphorus pesticides: fenitrothion, azinphos-ethyl, diazinon, fenthion and parathion-ethyl. Analysis of these pesticides at levels of 0.1 to 1 μg/l in the presence of natural interferences is achieved using automated on-line liquid-solid extraction (Prospekt) coupled to liquid chromatography and diode array detection followed by a recently developed multivariate self-modeling curve resolution method. The proposed approach uses only 100 ml of natural water sample and has improved resolution of the coeluted organophosphorus insecticides and their quantitation at trace level. The results have been compared with those obtained by different laboratories participating in the Aquacheck interlaboratory exercise (WRC, Medmenham, UK) where more conventional analytical techniques are being used. 相似文献
126.
Zdenek Slanina 《Theoretical chemistry accounts》1992,83(3-4):257-261
Summary The presence of several local energy minima on a potential hypersurface is treated in terms of geometry, energy, and harmonic vibrations. Partition functions of the minima are employed in order to treat temperature excitations of rotational-vibrational motions. Proportions of relative stabilities of the individual structures change with temperature (including interchanges of the relative stabilities so that the global energy minimum can even be less populated than a higher local energy minimum). Illustrative examples are given on B2H4 and Ga2H4 systems. The treatment is suggested as a standard complement of the local-minimum hypersurface representation (before whole potential hypersurfaces are constructed and employed in molecular dynamics treatments).Dedicated to Prof. Klaus Ruedenberg on the occasion of his 70th birthday 相似文献
127.
Interlaboratory comparsion exercises on the determination of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs) and dioxin-like polychlorinated biphenyls (PCBs) in three natural foodstuffs have been performed annually since 2000 by the Norwegian Institute of Public Health. Up to 77 laboratories from 24 countries world-wide have reported results. The data have been statistically analysed in order to assess the comparability of both the reported individual congener concentrations and the calculated toxic equivalents (TEQ). Due to the low concentrations of PCDDs/PCDFs and dioxin-like PCBs in food, the treatment of congeners reported as “not detected” and the identification of outliers, influence the estimation of the consensus values considerably. Based on the experiences from the first two rounds, an approach for calculation of the consensus values was established, resulting in a non-skewed distribution of data. The relative standard deviation of consensus TEQs was 13–32% for PCDDs/PCDFs and 11–45% for PCBs. Z-scores were calculated for PCDD/PCDF-TEQs using a target value of ±20% for the deviation. For food samples with a PCDD/PCDF contamination of more than half of the EU maximum level, 63–87% of the participants achieved Z-scores ±1, while for low contaminated foodstuffs about 60% of the participants had Z-scores of ±2. After four rounds of interlaboratory comparisons it can be concluded that there is a good comparability of the analytical data for dioxins and dioxin-like PCBs in food at higher contamination levels. However, the laboratories need to improve their performance when determining levels in food with low contamination of dioxin-like compounds, due to the increasing demand for analyses of such food items. The importance of determining dioxin-like PCBs is demonstrated by their large contribution to the total TEQ, especially in food from the marine environment. 相似文献
128.
The Horwitz curve states a relationship between the analyte concentration in various matrices and the interlaboratory reproducibility as found in collaborative studies. The reproducibility becomes worse (larger) with lowering of the analyte concentration. We found that the Horwitz assumption is too optimistic for analyses in plastics. Based on 15 different proficiency tests with 68 reproducibility-concentration relationships, it becomes clear that the precision can be worse by a factor of ten or more than predicted by the Horwitz curve. Organic analytes seem to be more critical than inorganic ones. One of the reasons is assumed to be the poor homogeneity of many samples. Another problem could be the lack of standard methods for plastics analyses. However, the great observed variability cannot be explained by these two features alone. 相似文献
129.
Michael Gluschke 《Accreditation and quality assurance》2006,11(8-9):470-473
This case study is written for laboratories in the German Marine Monitoring Program (GMMP) for the North and Baltic Seas in order to give support to the assessment of proficiency testing results for their external quality assurance. A second issue is to provide a practical, understandable and common way for the calculation of laboratory performance parameters, so-called combination scores. In this paper, the GMMP laboratory proficiency testing results of QUASIMEME (Quality Assurance of Information for Marine Environmental Monitoring in Europe) Laboratory Performance Studies for the last 5 years were reviewed. Combination scores for organochlorine pesticides and chlorinated biphenyls in marine sediment are presented and explained. However, the assessment approach is very general and should be applicable to most testing laboratories in the chemical field.Presented at the Eurachem PT Workshop September 2005, Portorož, Slovenia 相似文献
130.
Kaj Heydorn 《Accreditation and quality assurance》2008,13(12):723-724
The distribution of mutually consistent results from interlaboratory comparisons is expected to be leptokurtic, and readers
are warned against accepting conclusions based on simulations assuming normality.
Papers published in this section do not necessarily reflect the opinion of the Editors, the Editorial Board and the Publisher 相似文献