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61.
R. Becker Matthias Koch Sigrid Wachholz Tin Win 《Accreditation and quality assurance》2002,7(7):286-289
Due to the utilisation of 1,1,2-trichlorotrifluoroethane (CFE) as extraction solvent the IR-spectrometric determination of
total petrol hydrocarbon (TPH) in soil according to ISO/TR 11046 has been replaced by gas chromatography/flame ionisation
detection (GC/FID) after extraction with a halogen-free solvent according to ISO/DIS 16703:2001. The results obtained with
both methods by field laboratories in three proficiency testing (PT) rounds are compared. The consensus means obtained with
GC/FID are typically 10%–20% (ranging between 0% and 25%) higher than those found with IR-spectroscopy. On the contrary, coefficients
of variation (CV) are roughly double in case of GC/FID and are briefly discussed against the background of the Horwitz equation.
Received: 19 November 2001 Accepted: 17 March 2002 相似文献
62.
Fork 0 fixed we consider the joint distribution functionF
n
k
of then-k smallest order statistics ofn real-valued independent, identically distributed random variables with arbitrary cumulative distribution functionF. The main result of the paper is a complete characterization of the limit behaviour ofF
n
k
(x
1,,x
n-k) in terms of the limit behaviour ofn(1-F(x
n)) ifn tends to infinity, i.e., in terms of the limit superior, the limit inferior, and the limit if the latter exists. This characterization can be reformulated equivalently in terms of the limit behaviour of the cumulative distribution function of the (k+1)-th largest order statistic. All these results do not require any further knowledge about the underlying distribution functionF. 相似文献
63.
Leszek Klukowski 《Annals of Operations Research》1994,51(5):241-261
In this paper, some probabilistic properties of the nearest adjoining order (NAO) method are presented. They have been obtained under weaker assumptions than those commonly used, i.e. it is not assumed that comparisons are not independent and that probability of comparison errors are known. The results presented comprise the evaluation of the probability of obtaining an errorless solution with the use of the NAO method; asymptotic properties of this solution derived under the assumption that comparisons of different pairs (i.e. pairsx
i
,x
j
andx
r
,x
r
fori r,s andj r,s) are not correlated — for the case of one expert. An extension of results for the case ofN > 1 independent experts is also presented. This extension is accomplished by including an additional step — the aggregation of comparisons made by all experts for each pair of objects. Two ways of such an aggregation are analyzed: the averaging of experts' opinions and the majority principle. In the latter case, the result of the comparison is the same as the opinion of the majority of experts. The results obtained indicate an exponential convergence of the probability of the NAO solution to an errorless one in both cases. However, an application of the majority principle leads to a minimization problem, which is the same as in the case ofN = 1 and is much simpler than that corresponding to averaging of comparisons. 相似文献
64.
A. M. H. van der Veen A. J. M. Broos Anton Alink 《Accreditation and quality assurance》1998,3(11):462-467
In the interlaboratory study programme "ILS Coal Characterisation", eight interlaboratory studies were organised based on
the ISO standards for coal analysis. The use of blind samples in each round allows comparability of measurement results between
rounds to be assessed. Based on the results, it could be demonstrated that the vast majority of the measurement results of
the laboratories were traceable to results obtained in previous rounds of this programme. The hypothesis has been formulated
that the combined standard uncertainty obtained from an interlaboratory study is equal to the reproducibility standard deviation.
Whether the reproducibility can be used as the basis for the certification depends on whether the interlaboratory study includes
all effects to be taken into account for establishing an uncertainty statement.
Received: 12 April 1998 · Accepted: 2 July 1998 相似文献
65.
Interlaboratory evaluation of injection techniques for triglyceride analysis of cocoa butter by capillary gas chromatography 总被引:1,自引:0,他引:1
As part of two international collaborative studies, in which 14 laboratories applied capillary GLC to determine the triglyceride (TG) profile of cocoa butter, the performance of different sample introduction techniques, i.e. cold on-column injection (OCI), split injection and programmed-temperature vapouriser (PTV) injection, was compared. In both studies, the participants did not apply a uniform GLC procedure. Synthetic mixtures of triglycerides were chosen to permit an accurate determination of detector response factors. No statistically significant difference was found between the mean values obtained by different injection modes. The OCI, generally recommended as best practice, did not give superior results than the PTV or the split injection techniques. 相似文献
66.
Determination of ethyl carbamate in alcoholic beverages: an interlaboratory study to compare HPLC-FLD with GC-MS methods 总被引:3,自引:0,他引:3
de Melo Abreu S Alves A Oliveira B Herbert P 《Analytical and bioanalytical chemistry》2005,382(2):498-503
An international interlaboratory study on the determination of ethyl carbamate in alcoholic beverages by a new HPLC-FLD and by the official GC-MS methods is presented. The aim of this study was to improve the knowledge about precision and accuracy parameters of the new method and to compare the performance of both HPLC and GC methods. Five different samples representing table wines, fortified wines (red and white), distilled spirits, and wine spirits were available for analysis by each participant. Despite the low number of participants (6), the results obtained by the laboratories using the HPLC-FLD method are comparable to those obtained by GC-MS methods. The present study emphasizes the possibility to use, as routine, a much simpler analytical method than the current reference method by GC-MS for ethyl carbamate determination in alcoholic beverages. 相似文献
67.
Bunthoon Laongsri Cheerapa Boonyakong Nongluck Tangpaisarnkul Chainarong Cherdchu 《Accreditation and quality assurance》2007,12(3-4):194-200
It has not been long that metrology is well accepted as an important part in analytical chemistry since it helps the chemists
to receive the best measurement and accurate results with traceability. The National Institute of Metrology Thailand (NIMT),
which is a public agency under the supervision of the Ministry of Science and Technology, not only focuses on physical standards
but also provides and maintains standards in chemical field. pH measurement is one of the most widely used in the laboratories
including industries and medical area in Thailand. The chemical laboratory starts working on the project with the objective
of disseminating an accurate result in routine pH measurement. In 2002, the laboratory provided a service in calibration of
pH meter and organized the first local interlaboratory comparison program (NIMT–C-ILC-1: pH buffer) in pH measurement. There
were three buffer solution samples in the range of acid, neutral, and base. A total of 44 laboratories participated in this
program. The NIMT chemical laboratory also participated in the proficiency testing program that was conducted by PSB Corporation
Testing Group in Singapore. In 2003, NIMT started research in preparation of secondary buffers by using highly accurate pH
meters with glass electrode systems. The laboratory produced three secondary buffers, which were pH 4.01, 6.86, and 9.18 with
uncertainty 0.020 pH at 25°C. The competence of the laboratory was shown by the measurement results of the pilot study (APMP.QM-P06),
which was organized by the APMP electrochemical analysis working group (EAWG/TCQM) in 2005. The title of this study was “pH
determination of two phosphate buffers by Harned cell method and glass electrode method”. NIMT aims to achieve for establishment
of the primary method for pH measurement in the near future.
Presented at -- “BERM-10” -- April 2006, Charleston, SC, USA 相似文献
68.
Marina Patriarca Ferdinando Chiodo Marco Castelli Federica Corsetti Antonio Menditto 《Microchemical Journal》2005,79(1-2):337
The Me.Tos. Project, started in 1983 and still running, is an external quality assessment (EQA) scheme for laboratories performing specialized analyses in occupational and environmental laboratory medicine. Besides the organization of EQA exercises, initiatives for further education of the participants and the harmonization of EQA procedures at a European level are carried out. Participation in EQA schemes allows laboratories to comply with the international standards for the quality and competence of testing and clinical laboratories. The organization of the scheme includes the preparation of control materials, their distribution to the participants, according to strategies aimed to avoid identification of the samples, the statistical analysis of the results and the evaluation of laboratories' performance according to international guidelines and criteria set by the organizers. An overview of the scheme operation and the current performances of participants will be given. 相似文献
69.
The present situation of Japanese certified reference materials registered in the COMAR database 总被引:1,自引:0,他引:1
In the field of reference materials, COMAR (Code d'Indexation des Matériaux de Référence) is now internationally known as
a reliable directory. In order to improve the quality of COMAR, a document which covers general requirements for the registration
of reference material has recently been adopted by the Japanese coding centre, NITE. This paper describes the general requirements
for reference materials and the current status of the COMAR database coded by the National Institute of Technology and Evaluation
(NITE), Japan. The concept of the requirements is fundamentally based on the ISO Guides 30, 31, 33, 34 and 35. Certifications
of reference materials are divided into the following three categories in the newly adopted document.
1. Certifications based on the results of interlaboratory comparisons
2. Certifications in accordance with the Measurement Law
3. Certifications in accordance with the measurement results of national institutions
An example of an uncertainty evaluation is also presented in the paper.
Received: 14 October 1996 Accepted: 3 December 1996 相似文献
70.
The First Oxoferrate(I): On the Constitution of K3[FeO2] and K3[NiO2] Garnet-red single crystals of K3[FeO2] were obtained for the first time by heating intimate mixtures of K6[CdO4] and CdO (molar ratio 1:1.16) in closed Fe-cylinders at 450°C during 40 d. The same way of preparation via “reaction with the cylinder surface” was applied to prepare similarly coloured single crystals of K3[NiO2] (K6CdO4 in closed Ni-cylinders at 500°C during 49 d). The structure determination by four circle diffractometer data (MoKα , K3[FeO2]: 731 out of 731 Io(hkl), R = 5.76%, Rw = 5.33%, K3[NiO2]: 755 out of 755 Io(hkl), R = 8.70%, Rw = 4.25%) confirms the space groups P 41212 and P 43212, respectively. K3[FeO2]: a = 604.2(2) pm, c = 1 402.7(3) pm, Z = 4 K3[NiO2]: a = 603.6(1) pm, c = 1 405.2(2) pm, Z = 4. (powder data, standard deviations in parentheses) Essential feature of the structure are the dumb-bell-like anions [O? M? O]3? (M = Fe, Ni). Their arrangement corresponds to a stuffed derivative of the KrF2-type. Magnetic properties of K3[FeO2] were determined and cover the monovalence of Fe. MAPLE-calculations reveal the strong coincidence of monovalent VIIIb-cations. 相似文献