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Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement (v.5, #6)
Second Central European Conference on Reference Materials (CERM-2) Prague, Czech Republic, September 9–10, 1999
by Pavel Mader; Miloslav Suchánek (pp. 222-223).
Traceability of (values carried by) reference materials by P. De Bièvre (pp. 224-230).
Traceability is a property of the result of a measurement. Since values carried by (reference) materials must also have been obtained, of necessity, by measurement, the definition of traceability also applies to reference materials. It is extremely helpful to give the traceability (of the origin) of a reference material a separate name, i.e. 'trackability'. An analysis of the function of values carried by reference materials, shows that they can fulfill different functions, depending on the intended use. One of the functions located outside the traceability chain – and hence not very relevant for establishing traceability – is evaluating the approximate size of the uncertainty of the measurement of an unknown sample by performing a similar measurement on a reference material, used as a 'simulated sample'. Another function is located inside the traceability chain, where the reference material is used as an added 'internal standard'. Then, the value carried by the reference material is essential for establishing the traceability of the measured value of an unknown sample. In the latter application, the reference material acts as an 'amount standard' (the certified value for amount is used).
Keywords: Key words Traceability chain; Metrology in chemistry; Reference material; Amount standard; Validation
Some aspects of the evaluation of measurement uncertainty using reference materials by M. Buzoianu (pp. 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.
Keywords: Key words Measurement uncertainty; Reference materials; Turbidimetry
The preparation of a cabbage reference material for environmental monitoring and food analysis by S. Korhammer; Rolf Herzig; Peter Schramel; Jorma Kumpulainen; Bernd Markert; Herbert Muntau; Philippe Quevauviller (pp. 238-242).
Cabbage is frequently used in environmental monitoring and food control, and, hence, cabbage reference materials (RMs) are required for ensuring quality assurance. A cabbage RM was prepared in view of certification of specific elements from the "black list" of high toxicological interest and nutritive importance. All tasks of the RM production (production of the plant material, cutting and freeze-drying, determination of the residual water content, preparation of the RM, homogeneity testing, stability testing, certification measurements) are described in detail.
Keywords: Key words Production of CRMs; Bowen's kale; Residual water determination; Thallium
The use of certified reference materials in the Romanian traceability scheme by Steluta Duta (pp. 243-249).
For ensuring the traceability and uniformity of measurement results, the main objectives of national metrology programmes in chemistry are to calibrate and verify measuring instruments, to evaluate the uncertainty of measurement results and to intercompare the analytical results, etc. The concept of traceability has developed recently in chemical measurements, thus, an attempt to implement the principles of metrological traceability especially by appropriateness calibration using composition certified reference materials (CRMs) is underlined. Interlaboratory comparisons are also a useful response to the need for comparable results. The paper presents some aspects and practices in the field of spectrometric measurement regarding the metrological quality of the traceability by calibrating the instruments using suitable and reliable CRMs. The uncertainty of results, as a measure of the reliability that can be placed on them, has been adequately described in different documents and, as a consequence, some examples of evaluating the measurement uncertainty are described. The relationship between uncertainty and traceability, as two fundamental concepts of metrology which are intimately linked, is underlined.
Keywords: Key words CRMs; Spectrochemical measurements; Traceability
State of the art of third party product testing and certification:
by L. Thione; A. Pederneschi; E. Cirici; S. Helmprobst; B. Pecavar; B. Siegemund (pp. 250-253).
The role of the Czech Metrology Institute in the field of metrology in chemistry by Miloslav Suchánek; Jan Tichý (pp. 253-255).
The main role of a national metrological institute is to assure metrological traceability in the country. Metrology in chemistry is a developing field with specific features quite different from physical metrology and it is very difficult to establish a metrological system in chemistry based on the work of a single national institute, especially in small countries. For this reason the Czech Metrology Institute (CMI) has helped to establish the Association of National Reference Laboratories (METROCHEM) which is responsible for ensuring the traceability of chemical measurements in the Czech Republic. CMI is expected to carry out reference material certification (according to the Law on metrology) and develop special fields (electrochemistry, moisture and protein in grains).
Keywords: Key words Traceability; Reference material; National reference laboratories; Metrological institute; Law on metrology
New ISO Guide 34 – How is the change affecting practice in the Czech Republic? by J. Tichý (pp. 256-257).
The positive contribution of the ISO Guide 34 review is the idea of increasing responsibility of reference materials producers. The change of the main intention introduces some problems related to national legislation. There is a very important discussion going on about these problems among metrological bodies, accreditation institutes, reference material producers and laboratories.
Keywords: Key words ISO Guide 34; Certified reference material; Reference material producer; Law on metrology; Certifying body