共查询到20条相似文献,搜索用时 31 毫秒
1.
Michela Sega Elena Amico di Meane Francesca Rolle 《Accreditation and quality assurance》2009,14(11):601-605
Metrology in chemistry has its own features, which distinguish it from classical metrology: due to the lack of primary methods
applicable in routine measurements, metrological traceability of measurement results can be achieved by using in a proper
way suitable certified reference materials (CRMs), which can assure a direct relation to a reference. This article deals with
the activity of the Italian National Institute of Metrological Research (Istituto Nazionale di Ricerca Metrologica—I.N.Ri.M.)
on the analysis of various polychlorinated biphenyls congeners in organic solution by means of gas-chromatography coupled
with mass spectrometry. The metrological traceability approach in the quantification step is pursued via calibration solutions
prepared by gravimetrically diluting a CRM. The uncertainty for the calibration solutions was evaluated taking into account
all the relevant contributions. 相似文献
2.
M. Buzoianu 《Analytical and bioanalytical chemistry》2001,370(2-3):151-155
Several reference materials (RMs) and certified reference materials (CRMs) are widely used in Romania as measurement standards in different spectrochemical measurements. Among them, single element standard solution certified for their mass concentration play a key role in ensuring the required traceability of results expressed in this measurement unit. A short review of the locally available elemental RMs and CRMs used in atomic spectrometry or in other analytical techniques where aqueous standard solutions are required (usually called RMs or CRMs for spectrometry) is given. The experience of the INM in preparation and certification of such materials is described. Some aspects regarding their use for ensuring the accuracy and for confirmation of the traceability of analytical measurements, especially through calibration and metrological validation of main instrument performances, are discussed. 相似文献
3.
The two most important concepts in metrology are certainly “traceability to standards” and “measurement uncertainty evaluation”.
So far the questions related to these concepts have been reasonably solved in the metrology of “classical quantities”, but
for the introduction of metrological concepts in new fields, such as chemistry and biology, a lot of problems remain and must
be solved in order to support international arrangements. In this presentation, the authors want to develop the strategy implemented
at Laboratoire national de métrologie et d’essais (LNE) in metrology in chemistry and biology. The strategy is based on: (1)
pure solutions for calibration of analytical instruments, (2) use of certified reference materials (matrix reference materials),
and (3) participation to proficiency testing schemes. Examples will be presented in organic and inorganic chemistry. For laboratory
medicine, proficiency testing providers play an important role in the organization of External Quality Assessment Schemes.
For the time being, the reference value or the assigned value of the comparison is calculated with the results obtained by
the participants. This assigned value is not often traceable to SI units. One of the methods suggested by LNE is to ensure
the metrological traceability to SI units of the assigned value for the more critical quantities carried on analytes by implementing
the Joint committee for traceability in laboratory medicine reference methods. 相似文献
4.
Philip Taylor 《Accreditation and quality assurance》2004,9(1-2):24-32
An operational interlaboratory comparison programme is described which disseminates SI-traceable reference values to laboratories worldwide. These reference values have an uncertainty and traceability that is demonstrated at the highest metrological level. Participating laboratories can use these values to establish the degree of equivalence of their measurement results and can use this to support their measurement capability claims, e.g. towards third parties. The programme has been run by the Institute for Reference Materials and Measurements (IRMM) since 1988, in the first phase as an awareness programme. Currently, IRMM is focusing its efforts on educational aspects of metrology via a collaboration with the European Co-operation for Accreditation, national metrological institutes (NMIs) and interested academic networks. The viewgraphs used are presented in the “Electronic Supplementary Material” of this ACQUAL issue. 相似文献
5.
M Buzoianu 《Fresenius' Journal of Analytical Chemistry》2001,370(2-3):151-155
Several reference materials (RMs) and certified reference materials (CRMs) are widely used in Romania as measurement standards in different spectrochemical measurements. Among them, single element standard solution certified for their mass concentration play a key role in ensuring the required traceability of results expressed in this measurement unit. A short review of the locally available elemental RMs and CRMs used in atomic spectrometry or in other analytical techniques where aqueous standard solutions are required (usually called RMs or CRMs for spectrometry) is given. The experience of the INM in preparation and certification of such materials is described. Some aspects regarding their use for ensuring the accuracy and for confirmation of the traceability of analytical measurements, especially through calibration and metrological validation of main instrument performances, are discussed. 相似文献
6.
M. Buzoianu 《Accreditation and quality assurance》2000,5(6):231-237
In practice there are three aspects that need to be considered in order to achieve the required traceability according to
its definition: the 'stated reference', the 'unbroken chain of calibrations' and the "stated uncertainty". For a certain chemical
result, each of these aspects highly depends on the measurement uncertainty, both on its magnitude and how it was estimated.
Therefore, the paper describes the experience of the Romanian National Institute of Metrology in estimating measurement uncertainty
during the certification of reference materials (RMs), in metrological activities (calibration, pattern approval, periodical
verification, etc.), as well as during the analytical measurement process. Practical examples of estimation of measurement
uncertainty using RMs or certified reference materials are discussed for their applicability in spectrophotometric and turbidimetric
analysis. Use of the analysis of variance to obtain some additional information on the components of measurement uncertainty
and to identify the magnitude of individual random effects is described.
Received: 12 November 1999 / Accepted: 25 February 2000 相似文献
7.
Ilya Kuselman Francesca Pennecchi Cathy Burns Aleš Fajgelj Paolo de Zorzi 《Accreditation and quality assurance》2010,15(5):283-288
A metrological background for investigating out-of-specification (OOS) test results of chemical composition is discussed.
When an OOS test result is identified, it is important to determine its root causes and to avoid reoccurrence of such results.
An investigation of the root causes based on metrological concepts would be beneficial. It includes (1) assessment of validation
data of the measurement process, (2) evaluation of the measurement uncertainty contributions, and (3) assessment of metrological
traceability chains critical for measurement parameters and environmental conditions influencing the test results. The questions,
how can the validation data be applied for this investigation, and how can measurement uncertainty contributions and/or metrological
traceability chains change a probability of OOS test results, are analyzed. 相似文献
8.
Purity certified reference materials (CRMs) are playing a key role in metrological traceability, because they form the basis
for many traceability chains in chemistry. Recently, the National Metrology Institute of Japan (NMIJ) has developed two purity
CRMs for creatinine (NMIJ CRM 6005-a) and urea (NMIJ CRM 6006-a), because the concentrations of these two compounds are frequently
measured in clinical laboratories for monitoring the renal functions. In the certification of purity CRMs, it is essential
that the materials have been thoroughly characterized for purity, and the purity should preferably be determined directly
by a primary method of measurements. In the development of these two CRMs, we used the purified materials as candidates. The
certified values were assigned based on the results of two different methods; acidimetric titration and nitrogen determination
by the Kjeldahl method. Since both methods cannot distinguish some impurities from the target compounds, major impurities
in the candidate materials were also identified, quantified, and subtracted. These CRMs can provide a traceability link between
routine clinical methods and SI units.
Presented at BERM-11, October 2007, Tsukuba, Japan. 相似文献
9.
10.
This paper discusses the basis and historical development of the traceability chain for pH. The quantity pH, first introduced
in 1909, is among the most frequently measured analytical quantities. The practical measurement of the pH value of a sample
is inexpensive, easy to perform, and yields a rapid result. However, the problems posed by the traceability of pH are not
easy to solve. Most pH measurements are performed by potentiometry, using a glass electrode as the pH sensor. Such pH electrodes
must be calibrated at regular intervals. Confidence in the reliability of pH measurements requires establishment of a metrological
hierarchy including an uncertainty budget for calibration that links the pH measured in the sample to an internationally agreed
and stated reference. For pH, this reference is the primary measurement of pH. A traceability chain can be established that
links field measurements of pH to primary buffer solutions that are certified using this primary method. This allows the user
in the field to estimate the measurement uncertainty of the measured pH data. As the realization of the primary measurement
is sophisticated and time-consuming, primary standards are generally realized at national metrology institutes. A number of
potentiometric methods are suitable for the determination of the pH of reference buffer solutions by comparison with the primary
standard buffers. The choice between the methods should be made according to the uncertainty required for the application.
For reference buffer solutions that have the same nominal composition as the primary standard, the differential potentiometric
cell, often called the Baucke cell, is recommended. 相似文献
11.
G. Price 《Accreditation and quality assurance》1996,1(2):57-66
National measurement systems are infrastructures to ensure, for each nation, a consistent and internationally recognised
basis for measurement. Such complex systems have historical, technical, legal, organisational and institutional aspects to
connect scientific metrology with practical measurements. Underlying any valid measurement is a chain of comparisons linking
the measurement to an accepted standard. The ways the links are forged and the etalons (measurement standards) to which they
connect are defining characteristics of all measurement systems. This is often referred to as traceability which aims at basing
measurements in common measurement units – a key issue for the integration of quantitative chemical analysis with the evolving
physical and engineering measurement systems. Adequate traceability and metrological control make possible new technical capabilities
and new levels of quality assurance and confidence by users in the accuracy and integrity of quantitative analytical results.
Traceability for chemical measurements is difficult to achieve and harder to demonstrate. The supply of appropriate etalons
is critical to the development of metrology systems for chemical analysis. An approach is suggested that involves the development
of networks of specialised reference laboratories able to make matrix-independent reference measurements on submitted samples,
which may then be used as reference materials by an originating laboratory using its practical measurement procedures.
Received: 31 July 1995 Accepted: 19 August 1995 相似文献
12.
S. Duta Y. Aregbe L. Van Nevel P. Taylor F. Iacobescu 《Accreditation and quality assurance》2006,10(10):554-561
On the basis of quantitative chemical measurements many important decisions are made in support of legislation or in industrial processes or social aspects. For this reason it is important to improve the quality of chemical measurement results and thus make them comparable and acceptable everywhere. The measurement quality is important to enable an equivalent implementation of the European Union regulations and directives across an enlarged EU. In this context, the European Commission–Joint Research Centre–Institute for Reference Materials and Measurement (EC-JRC-IRMM) set up a programme to improve the scientific basis for metrology in chemistry (MiC) in EU candidate countries in the framework of EU enlargement. Several activities were initiated, such as training, fellowships, sponsoring of seminars, conferences and participation in interlaboratory comparisons. To disseminate measurement traceability, IRMM provides through its International Measurement Evaluation Programme (IMEP) an interlaboratory tool to enable the benchmarking of laboratory performance. IMEP emphasizes the metrological aspects of measurement results, such as traceability and measurement uncertainty. In this way it has become a publicly available European tool for MiC. The Romanian Bureau of Legal Metrology – National Institute of Metrology (BRML-INM) actively supports the participation of Romanian authorized and field laboratories in IMEP interlaboratory comparisons. This paper describes the interest of Romanian laboratories participating in this programme, the analytical and metrological problems that became relevant during these exercises and some actions for improvement. The results from Romanian laboratories participating in IMEP-12 (water), IMEP-16 (wine), IMEP-17 (human serum) and IMEP-20 (tuna fish) are presented. To conclude, the educational and training activities at national level organized jointly by the Romanian National Institute of Metrology (INM) and IRMM are also mentioned. 相似文献
13.
Alex Williams 《Accreditation and quality assurance》2001,6(2):73-75
Establishment of the traceability and the evaluation of the uncertainty of the result of a measurement are essential in order
to establish its comparability and fitness for purpose. There are both similarities and differences in the way that the concepts
of traceability and uncertainty have been utilised in physical and chemical measurement. The International Committee of Weights
and Measures (CIPM) have only in the last decade set up programmes in chemical metrology similar to those that have been in
existence for physical metrology for over a century. However, analytical chemists over that same period have also developed
techniques, based on the concepts of traceability and uncertainty, to ensure that their results are comparable and fit for
purpose. This paper contrasts these developments in physical and chemical metrology and identifies areas where these two disciplines
can learn from each other. 相似文献
14.
Steluţa Duţă 《Analytical and bioanalytical chemistry》2001,370(2-3):147-150
This paper discusses some aspects of the use of certified reference materials (CRMs) to ensure the uniformity of results, especially through calibration and validation of spectro(photo)metric instrument performance. In this way the link between the intrinsic performance of instruments and the accuracy of measurement results is underlined. Some types of local CRM are also presented. 相似文献
15.
S Dut? 《Fresenius' Journal of Analytical Chemistry》2001,370(2-3):147-150
This paper discusses some aspects of the use of certified reference materials (CRMs) to ensure the uniformity of results, especially through calibration and validation of spectro(photo)metric instrument performance. In this way the link between the intrinsic performance of instruments and the accuracy of measurement results is underlined. Some types of local CRM are also presented. 相似文献
16.
M. Buzoianu 《Accreditation and quality assurance》2000,5(4):142-150
The basic concepts of traceability as they are defined by the Comité Consultatif pour la Quantité de Matière (CCQM) are difficult
to apply to some chemical results. For instance, for some environments or chemical analyses measurement results are expressed
in conventional units. Such units are realized on conventional scales relying on two fundamental pillars: reference materials
and standard specification. The octane number of fuel or water turbidity measurements are typical examples of such units.
Traceability concepts are discussed in terms of their practical applicability for turbidimetric analysis. Some outcomes on
the validation of the metrological performance of turbidimeters and the comparability of turbidity measurement results are
also presented.
Received: 8 June 1999 / Accepted: 13 December 1999 相似文献
17.
18.
Current developments in Germany for establishing a traceability system for chemical measurements are reported. The focus is on a dissemination mechanism which employs chemical calibration laboratories accredited within the framework of the German Calibration Service (DKD) and acting as "multipliers" between the national standards level and the user level by providing the user with calibration means which are traceable to the SI via national standards. At the national standards level, a network of high-level chemistry institutes coordinated by the national metrology institute, PTB, provides the primary references for chemical measurements.The use of the metrological dissemination system provided by the DKD also for chemical measurements is a logical extension of a traceability mechanism, successful for more than two decades in general metrology, to metrology in chemistry. In detail, traceability structures in clinical chemistry, electrochemistry, elemental analysis and gas analysis are described. This system has become an important part of the efforts made in Germany to support chemical laboratories in meeting the traceability requirements of the market and of legal regulations. 相似文献
19.
Since the uncertainty of each link in the traceability chain (measuring analytical instrument, reference material or other
measurement standard) changes over the course of time, the chain lifetime is limited. The lifetime in chemical analysis is
dependent on the calibration intervals of the measuring equipment and the shelf-life of the certified reference materials
(CRMs) used for the calibration of the equipment. It is shown that the ordinary least squares technique, used for treatment
of the calibration data, is correct only when uncertainties in the certified values of the measurement standards or CRMs are
negligible. If these uncertainties increase (for example, close to the end of the calibration interval or shelf-life), they
are able to influence significantly the calibration and measurement results. In such cases regression analysis of the calibration
data should take into account that not only the response values are subjects to errors, but also the certified values. As
an end-point criterion of the traceability chain destruction, the requirement that the uncertainty of a measurement standard
should be a source of less then one-third of the uncertainty in the measurement result is applicable. An example from analytical
practice based on the data of interlaboratory comparisons of ethanol determination in beer is discussed.
Received: 5 October 2000 Accepted: 3 December 2000 相似文献
20.
John L. Love 《Accreditation and quality assurance》2002,7(3):95-100
Chemical results normally involve traceability to two reference points, the specific chemical entity and the quantity of this
entity. Results must also be traceable back to the original sample. As a consequence, any useful estimation of uncertainty
in results must include components arising from any lack of specificity of the method, the variation between repeats of the
measurement and the relationship of the result to the original sample. Chemical metrology does not yet incorporate uncertainty
arising from any lack of specificity from the method selected or the traceability of the result to the original sample. These
sources of uncertainty may however have much more impact on the reliability of the result than will any uncertainty associated
with the repeatability of the measurement. Uncertainty associated with sampling may amount to 50–1000% of the reported result.
Chemical metrology must be expanded to include estimations of uncertainty associated with lack of specificity and sampling.
Received: 29 May 2001 Accepted: 17 December 2001 相似文献