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1.
P. Armishaw J. M. Majewski P. J. McLay R. G. Millar 《Fresenius' Journal of Analytical Chemistry》1998,360(6):630-639
Beef fat samples were prepared and tested as candidate reference materials for organochlorine and organophosphorus pesticides.
The CRMs consisted of beef fat spiked with pesticide solutions. One sample (ACSL CRM 1) was prepared containing close to 0.2
mg/kg of each of the organochlorine pesticides dieldrin and heptachlor epoxide. A second sample (ACSL CRM 2) was prepared
containing close to 0.8 mg/kg of each of the organophosphorus pesticides diazinon, chlorpyrifos and ethion. The spiking levels
and homogeneity of the materials were verified. The coefficients of variation of 5 analyses carried out to test between-jar
homogeneity for each reference material were dieldrin, 3.5%; heptachlor epoxide, 1.1%; diazinon, 2.1%; chlorpyrifos, 1.2%
and ethion, 3.1%. No instability in any of these compounds was detected over a twelve month period. The candidate reference
materials were found to be suitable for certification by interlaboratory testing.
The certification process was based on a two-stage nested design described in ISO Guide 35. Analysis of results reported by
collaborating laboratories provided an assessment of the homogeneity of the reference materials. The certified values together
with their upper and lower 95% confidence limits are:
ACSL CRM 1*Dieldrin*0.199 mg/kg
**(0.188,
**0.210 mg/kg)
*Heptachlor epoxide*0.194 mg/kg
**(0.176,
**0.212 mg/kg)
ACSL CRM 2*Diazinon*0.805 mg/kg
**(0.755,
**0.855 mg/kg)
*Chlorpyrifos*0.790 mg/kg
**(0.728,
**0.852 mg/kg)
*Ethion*0.813 mg/kg
**(0.746,
**0.879 mg/kg).
A certificate for each material was prepared according to the guidelines set out in ISO Guide 31.
Received: 25 April 1997 / Revised: 19 August 1997 / Accepted: 28 August 1997 相似文献
2.
Yuri A. Karpov Natella A. Arakelian V. E. Kvin Vasilisa B. Baranovskaya Tatyana Yu Alekseeva V. P. Obresumov Lyudmila P. Zhitenko 《Accreditation and quality assurance》2001,6(2):66-71
Our experience of executing proficiency testing programs on the analysis of precious metals and precious metal bearing materials
is summarized. Six proficiency testing programs of the ”distributed sample testing” type were carried out using samples essentially
distinct from each other: (I) certified samples of fine gold and fine silver, and (II) recoverable raw (scrap and catalyst
waste) containing precious metals of unknown contents. The test results were assessed using the London Bullion Market Association
(LBMA) rules and by Z-criteria using the ISO/IEC Guide 43 scale. Satisfactory results were presented by all participants for the analysis of certified
samples of fine gold and fine silver. The results of catalyst waste analysis agreed rather well, whereas the scrap analysis
revealed an essential discrepancy in the data for some samples. The reasons for such discrepancies are discussed.
Received: 9 June 2000 Accepted: 21 November 2000 相似文献
3.
A. Rabinovitch 《Accreditation and quality assurance》2002,7(11):473-476
The College of American Pathologists (CAP) operates voluntary programs in proficiency testing (PT) and quality monitors, which
are briefly described. Additionally, a peer-based laboratory accreditation program covers over 6,100 clinical laboratories.
Participation requires successful PT and on-site inspections using a series of 18 checklists structured along traditional
subdisciplines of laboratory medicine and anatomic pathology. The laboratory general checklist contains over 250 questions
covering broad issues affecting all disciplines. Among these are three items within the computer services section that specifically
probe the laboratory’s use of autoverification. Data autoverification is defined as the process by which the computer performs
the initial verification of test results; any data that fall outside of set parameters should be reviewed by the human operator.
Central to these questions is the role of the laboratory director in approving the rules and validation. CAP does not define
the specific technical details, recognizing the uniqueness of each laboratory setting and the patients it serves.
Received: 8 August 2002 Accepted: 10 August 2002
Presented at the European Conference on Quality in the Spotlight in Medical Laboratories, 7–9 October 2001, Antwerp, Belgium
Correspondence to A. Rabinovitch 相似文献
4.
Density functional theory, in combination with a) a careful choice of the exchange-correlation part of the total energy and b) localized basis sets for the electronic orbitals, has become the method of choice for calculating the exchange-couplings
in magnetic molecular complexes. Orbital expansion on plane waves can be seen as an alternative basis set especially suited
to allow optimization of newly synthesized materials of unknown geometries. However, little is known on the predictive power
of this scheme to yield quantitative values for exchange coupling constants J as small as a few hundredths of eV (50–300 cm−1). We have used density functional theory and a plane waves basis set to calculate the exchange couplings J of three homodinuclear Cu-based molecular complexes with experimental values ranging from +40 cm−1 to −300 cm−1. The plane waves basis set proves as accurate as the localized basis set, thereby suggesting that this approach can be reliably
employed to predict and rationalize the magnetic properties of molecular-based materials.
Corresponding author. E-mail: Carlo.Massobrio@ipcms.u-strasbg.fr
Received August 5, 2002; accepted August 9, 2002 相似文献
5.
The role of matrix reference materials in the process of demonstrating the degree of equivalence of measurement results obtained
from intercomparisons is outlined, reviewing exemplary selected experience gained at BAM regarding the determination of organic
contaminants in environmental matrices.
The specific characteristics of reference materials employed in the process of demonstrating equivalence between laboratories
in the course of proficiency testing as well as the development, comparison and validation of methods are elaborated. The
demand is for series of appropriately characterised samples which are fit for the purpose and it is seen from representative
examples that the utilisation of such tailor-made RM designed to tackle the specific need of an analytical problem dominates
over certified matrix reference materials in this context. Concluding, the role of certified matrix reference materials in
quality assurance is briefly looked at both from the user’s and providers’ points of view.
Received: 9 September 2002 Accepted: 16 December 2002
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 R. Becker 相似文献
6.
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
7.
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
8.
B. Röhl-Kuhn K. Meyer P. Klobes T. Fritz 《Analytical and bioanalytical chemistry》1998,360(3-4):393-397
Porous and finely dispersed certified reference materials (CRM) were certified using the gas adsorption method. The special
certification procedure for IUPAC isotherm classification types I, II, and IV is presented for meso- and macroporous materials
with special emphasis on specific surface area, specific pore volume and pore width according to standards DIN 66 131, 66
134, and 66 135. Four CRMs (SiO2, α-Al2O3, two transition aluminas) with a macro- and mesopore range are presented. Certification was made on the basis of BCR guidelines
in connection with interlaboratory tests (altogether 38 participating laboratories, 44 various gas adsorption apparatus).
Received: 25 April 1997 / Revised: 22 August 1997 / Accepted: 28 August 1997 相似文献
9.
B. Gawlik Martine Druges Michele Bianchi Angelo Bortoli Antonius Kettrup Herbert Muntau 《Fresenius' Journal of Analytical Chemistry》1997,358(3):441-445
The quality of the aquatic and marine environment can be monitored by the determination of pollutants in organisms living
in this environment. Certified reference materials and well-organised proficiency tests are powerful means of ensuring a constant
level of quality and verifying the correct application of standardised methods. The preparation of a tuna fish proficiency
testing material for the evaluation of quality of As and Hg monitoring in seafood is described. Preparation and characterisation
of the material as well as studies on its homogeneity and stability are described. Concentrations of 3.4 ± 0.2 mg/kg total
arsenic and 2.91 ± 0.09 mg/kg total mercury have been determined as target values. Moreover indicative values for some trace
elements (Cd, Cu, Ni, Pb, Sr) and some major constituents (Al, Br, C, Ca, Cl, Fe, H, K, Mg, N, Na, P, S, Si, Zn) have also
been measured.
Received: 29 November 1996 / Revised: 17 February 1997 / Accepted: 22 February 1997 相似文献
10.
Ian Robert Juniper 《Accreditation and quality assurance》1999,4(8):336-341
Proficiency testing is a means of assessing the ability of laboratories to competently perform specific tests and/or measurements.
It supplements a laboratory's own internal quality control procedure by providing an additional external audit of their testing
capability and provides laboratories with a sound basis for continuous improvement. It is also a means towards achieving comparability
of measurement between laboratories. Participation is one of the few ways in which a laboratory can compare its performance
with that of other laboratories. Good performance in proficiency testing schemes provides independent evidence and hence reassurance
to the laboratory and its clients that its procedures, test methods and other laboratory operations are under control. For
test results to have any credibility, they must be traceable to a standard of measurement, preferably in terms of SI units,
and must be accompanied by a statement of uncertainty. Analytical chemists are coming to realise that this is just as true
in their field as it is for physical measurements, and applies equally to proficiency testing results and laboratory test
reports. Recent approaches toward ensuring the quality and comparability of proficiency testing schemes and the means of evaluating
proficiency test results are described. These have led to the drafting of guidelines and subsequently to the development of
international requirements for the competence of scheme providers.
Received: 2 January 1999 · Accepted: 7 April 1999 相似文献
11.
P. J. S. Barbeira Nelson R. Stradiotto 《Fresenius' Journal of Analytical Chemistry》1998,361(5):507-509
The simultaneous “in natura” determination of trace Zn, Pb and Cu in whisky samples by anodic stripping voltammetry (ASV), using a hanging mercury drop
electrode, without previous treatment or addition of supporting electrolyte is described. The choice of an appropriate stripping
voltammetric method and deposition potential minimizes the influence of the organic content and ensures a good reproducibility
of the measurements. The reliability of the method was tested comparing the results with those of atomic absorption spectroscopy
(AAS), with differences of about 10%. The method allows the determination of heavy metal ions in the μg L–1 range.
Received: 14 August 1997 / Revised: 10 December 1997 / Accepted: 11 December 1997 相似文献
12.
Kaj Heydorn 《Accreditation and quality assurance》2006,10(9):479-484
Proficiency data with stated uncertainties represent a unique opportunity for testing that the reported uncertainties are consistent with the Guide to the expression of uncertainty in measurement (GUM). In most proficiency tests, however, this opportunity is forfeited, because proficiency data are processed without regard to their uncertainties. In this paper we present alternative approaches for determining a reference value as the weighted mean of all mutually consistent results and their stated uncertainties. Using an accepted reference value each reported uncertainty estimate can be expressed as an E
n
number, but a value of confirms its validity only if the uncertainty of the reference value is negligible in comparison.Reference values calculated for results from an International Measurement Evaluation Programme (IMEP-9) by “bottom up” as well as “top down” methods were practically identical, although the first strategy yielded the lowest uncertainty. A plot of individual coefficients of variation (CV) versus E
n
numbers helps interpretation of the proficiency data, which could be used to validate relative uncertainties down to <1%. 相似文献
13.
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
14.
A proficiency testing programme might involve a great number of participating laboratories coming from different countries or regions, and normally they analysed the same test materials using their own routine analytical methods. Hence, the results of a proficiency testing programme may contain valuable information which could serve purposes other than just performance evaluation. This study attempted to extract information from the results of a proficiency testing programme for the purposes of educating the participating laboratories as suggested by ISO/IEC 17043. The “bias analysis” approach introduced in this study was based on the statistical model of measurement and the nature of bias in chemical analysis. With this approach, the participating laboratories could estimate the bias associated with different settings of experimental conditions according to the statistics of subset distribution of the reported results from the participating laboratories. This would be useful for them to review the analytical procedures they used and modify their methods if needed. The approach was applied to the analysis of data obtained from a number of past proficiency testing programmes, and the findings were discussed in this paper. 相似文献
15.
G. Meissner Kari Hartonen M.-L. Riekkola 《Fresenius' Journal of Analytical Chemistry》1998,360(5):618-621
A method is developed for the determination of β-blockers in serum and urine at levels of 0.5 μg/mL. The technique uses a
combination of solid phase extraction (SPE) with in situ derivatization and supercritical fluid extraction (SFE) with subsequent
gas chromatography mass spectrometry. The optimization of the SFE step shows that a static extraction period can be eliminated.
The method gives good linearity (r = 0.991–0.999) and repeatability in the concentration range of 0.5 to 5 μg/mL. Relative
standard deviations for oxprenolol, propanolol and metoprolol were less than 5% in serum and 5–11% in urine.
Received: 23 May 1997 / Revised: 28 July 1997 / Accepted: 5 August 1997 相似文献
16.
Anodic stripping voltammetric determination of total lead, copper and selenium in whole blood and blood serum 总被引:1,自引:0,他引:1
A two-step procedure including appropriate wet-digestions, separation of selenium from interfering ions such as heavy metal
ions with pentyl alcohol and anodic stripping voltammetric (ASV) determination of Pb2+, Cu2+ and SeO3
2– is developed. The elements in digested whole blood and serum sample solutions were determined by using a standard addition
method. 1 × 10–9 mol/L SeO2–
3, Cu2+ and Pb2+ were successfully determined with relative standard deviations of approximately 1–2% (n = 6–8).
Received: 19 August 1996 / Revised: 24 February 1997 / Accepted: 28 February 1997 相似文献
17.
R. v. Hentig T. Goldbrunner F. v. Feilitzsch G. Angloher 《Fresenius' Journal of Analytical Chemistry》1998,360(6):664-668
For the determination of trace elements in organic liquids radiochemical neutron activation analysis has been combined with
counting methods geared to various decay modes of indicator radionuclides leading to a high sensitivity required for ultrapure
samples. The activation parameters such as irradiation time, sample mass and neutron flux have been enlarged to the maximum
possible in the available irradiation facility. Separation yields and adsorption losses have been studied in detail for a
set of elements in order to rule out losses during the separation process. The attainable limits of detection are 2 · 10–16g/g for U and Lu, in the 5 · 10–15g/g range for Th and Sm, in the 1 · 10–14g/g region for La, 5 · 10–13g/g for Rb, Cd and 2 · 10–12g/g for K and In. Although the analysis focused on traces of naturally occurring radioisotopes, results for Cr, Fe, W and
Zn are presented as well.
Received: 14 May 1997 / Revised: 28 August 1997 / Accepted: 9 September 1997 相似文献
18.
A new, simple, selective and sensitive method for the spectrophotometric determination of antimony in rain water is described.
It includes preconcentrating Sb with surfactants (i.e. cetylpyridinium chloride (CPC) and Triton X-100 (TX-100)) into toluene
and allowing the extract to react with a dye, i.e. brilliant green (BG). The value of apparent molar absorptivity is 5.55
× 105 L-mol–1· cm–1 at λmax = 620 nm; the detection limit is 3 ng/mL Sb in rain water at 3-fold preconcentration.
Received: 6 June 1997 / Revised: 1 August 1997 / Accepted: 5 August 1997 相似文献
19.
A new and efficient Hg(II) back-elution method for the desorption of Cd, Cu, and Pb from Chelex-100 chelating resin was developed.
A smaller eluent volume and shorter elution time can be achieved using an Hg(II) containing eluent rather than pure nitric
acid. Owing to the remaining Hg(II) ion in the effluent, a mercury thin-film electrode is formed in-situ during the anodic
stripping voltammetric determination without any further addition of Hg(II). The results indicate that all the analytes in
seawater matrix can be completely adsorbed on Chelex-100 resin from the sample at pH 6.5, and subsequently eluted from the
resin with an acid solution of 5 × 10–4 mol/L Hg2+ + 1 mol/L HClO4. The detection limits obtained from the differential-pulse anodic (μg L–1 to ng L–1) stripping voltammetry are at sub-ppb to ppt (μg L–1 to ng L–1) levels permitting to determine Cd, Cu and Pb traces in seawater. The analytical reliability was confirmed by the analysis
of the certified reference material CASS-II (open ocean seawater).
Received: 22 April 1997 / Revised: 5 August 1997 / Accepted: 7 August 1997 相似文献
20.
Optimization of virtual orbitals in the framework of a multiconfiguration spin-coupled wave function
Nick J. Clarke Mario Raimondi Maurizio Sironi Joseph Gerratt David L. Cooper 《Theoretical chemistry accounts》1998,99(1):8-17
A new method is introduced for the optimization of nonorthogonal virtual orbitals for use in general multiconfiguration spin-coupled wave functions. The use of a number of highly effective approximations greatly reduces the computational effort
involved, the most important being the use of a second-order perturbation expression for the energy and an approximate expression
for the elements of the Hessian. As a result, the overall scheme scales very favourably with respect to the numbers of active
electrons and of basis functions, making it suitable for the accurate study of large systems. Benchmark calculations are presented
for the dissociation of LiH(X1Σ+) and Li2(X1Σ+
g
) using a highly compact four-configuration wave function. Standard spin-coupled valence bond expansions in the same virtual
space are required to be significantly larger before equivalent results are obtained. The results are shown to compare very
favourably with full valence complete active space self-consistent field calculations using an identical basis, and binding
energies are within 4% of the values obtained from full configuration interaction calculations in the same basis set.
Received: 10 June 1997 / Accepted: 7 October 1997 相似文献