Accreditation and Quality Assurance (v.16, #10)

Definitions of ‘measurement’ by René Dybkaer (479-482).
In spite of the fundamental importance of the concept ‘measurement’ in the description of our world, there is found an amazing number of very different definitions, even in publications from ISO and IEC, both regarding terminography and selection of characteristics. Of special interest are the choices between relations to single true values or a distribution, inclusion of nominal properties or not, and whether ‘measurement’ is a process or an outcome. These problems should be settled before the production of the fourth edition of the International vocabulary of metrology (VIM), and different possible generic concept diagrams are being discussed.
Keywords: Definition; Measurement; Nominal property; Terminography; True value

Dark uncertainty by Michael Thompson; Stephen L. R. Ellison (483-487).
Standard uncertainties obtained by the GUM approach for a range of analytical methods are compared directly and indirectly with estimates of reproducibility standard deviation for the same methods. Results were obtained from both routine analysis and international key comparisons. A general tendency for the uncertainty to be substantially less than the reproducibility standard deviation was found.
Keywords: Uncertainty; Dark uncertainty; Reproducibility conditions; GUM

Metrological concept for comparable measurement results under the European water framework directive: demonstration of its applicability in elemental analysis by Detlef Schiel; Olaf Rienitz; Reinhard Jährling; Bernd Güttler; Ralf Matschat; Holger Scharf; Jürgen Birkhahn; Guillaume Labarraque; Paola Fisicaro; Ulrich Borchers; David Schwesig (489-498).
Within the scope of a project of the “European Association of National Metrology Institutes” (EURAMET), a European metrological dissemination system (network) providing traceable reference values assigned to matrix materials for validation purposes is described and put to the test. It enables testing laboratories (TL) to obtain comparable results for measurements under the “EU Water Framework Directive 2000/60/EC” (WFD) and thus, to comply with a core requirement of this very directive. The dissemination system is characterized by the fact that it is available to all laboratories throughout Europe which intend to perform measurements in the context of the WFD and that it can ensure sustainable metrological traceability to the International System of Units (SI) as a reference point for the measurement results. This dissemination system is set up in a hierarchical manner and links up the level of the national metrology institutes (NMI) with that of the TLs via an intermediate level of calibration laboratories (CL) by comparison measurements. The CLs are expert laboratories with respect to the measurement of the analytes considered here (within the project, the CLs are called potential calibration laboratories (PCL)) and are additionally involved in the organization of comparison measurements within the scope of regional quality assurance (QA) systems. Three comparison measurements have been performed to support the approach. A total of about 130 laboratories participated in this exercise with the focus on the measurement of the priority substances Pb, Cd, Hg, and Ni defined in the WFD. The elemental concentrations in the water samples roughly corresponded to one of the established environmental quality standards (EQS), the annual average concentration (AA-EQS), which is defined in the daughter Directive 2008/105/EC of the WFD. It turned out that a significant number of TLs still need to improve their measurement methods in order to be able to fulfill the minimum requirements of the WFD, in particular, with regard to the elements Cd and Hg probably due to their low EQS values. Furthermore, it became obvious that the hierarchical dissemination system suggested here actually corresponds to the measuring capabilities of the three participating groups (NMIs, PCLs, and TLs).
Keywords: Metrology; Metrological traceability; Comparability; Elemental analysis; Water framework directive

The results of and findings from an interlaboratory comparison among laboratories carrying out food testing of pesticide residues in the APEC (Asia–Pacific Economic Cooperation) region are presented and discussed to show critical roles of chemical metrology infrastructure in establishing traceability of measurements and in supporting existing measurement capability in safety and quality of food trade. The study material, which was prepared and certified by Korea Research Institute of Standards and Science (KRISS), was freeze-dried Chinese cabbage powder fortified with two organophosphorous pesticides (diazinon and chlorpyrifos). Among 14 participants, 12 laboratories were accredited based on ISO/IEC17025 and one laboratory was under assessment for the accreditation at the time of this study. Though all participants demonstrated very good intra-day repeatability and inter-day intermediate precision, many of them showed a large bias from the certified values. It is suggested that in addition to the accreditation system, economies are encouraged to develop appropriate chemical metrology infrastructure, which could effectively support laboratories to assure measurement traceability to SI, for which NMIs could play significant roles through their metrological services recognized in Mutual Recognition Arrangement (MRA) of the International Committee for Weights and Measures (Comité International des Poids et Mesures, CIPM).
Keywords: Interlaboratory comparison; Chemical metrology; Traceability; Chinese cabbage; Pesticide residue

A proficiency test scheme for the quality control of black tea and development of quality control material for internal quality control by Cemalettin Baltacı; Huri İlyasoğlu; Sevim Beyza Öztürk Sarıkaya; Sevda Cavrar; Nurettin Yaylı (507-513).
A proficiency test (PT) was organized for quality control analysis of black tea. Test materials for the analyses of total content of powder tea, moisture, total ash, acid-insoluble ash, water-soluble ash, alkalinity of water-soluble ash, water extract, crude fiber and caffeine were sent to the participant laboratories (n:43) in 2009. The assigned value, standard deviation of the parameters and z-scores of the participant laboratories were calculated using the data reported by the participants. The percentage of the reported results for analytes was found to be ranged from 67.5 to 100%. Acceptable z-scores were achieved by 80.5–97.5% of the participant laboratories. More than 15% of unacceptable results were obtained for acid-insoluble ash and caffeine analyses. The quality control material for quality control analysis of black tea was developed from the remaining material.
Keywords: Black tea; Proficiency test; Quality control material; z-score

Results and effects of homogeneity and stability studies carried out by X-ray fluorescence on the new reference material BAM-H010 by Markus Ostermann; Achim Berger; Christian Mans; Christoph Simons; Stephanie Hanning; Anton Janßen; Martin Kreyenschmidt (515-522).
The Federal Institute for materials research and testing (BAM) in cooperation with the Fachhochschule Münster has developed a new certified polymeric reference material, BAM-H010. The reference material consists of acrylonitrile–butadiene–styrene terpolymer (ABS) and has been doped with different contents of the elements Br, Cd, Cr, Hg and Pb. The monitoring of these elements is demanded in the EU directive 2002/95/EG, commonly referred to as RoHS. We have shown that the uncertainty contribution of the thermal long-term stability (u stability) is negligible compared to the contribution to the uncertainty caused by the method used for the characterization of the elemental content and the batch inhomogeneity (u homogeneity). The stability of the ABS material during exposure of the samples with hard X-radiation leads to a degradation of the ABS matrix with either long- or short-chain products.
Keywords: Reference material; Plastic; RoHS; WEEE; X-ray fluorescence

This paper demonstrates the use of the multivariate analysis for the quick and easy evaluation of the experimental results from the homogeneity test of two new certified reference materials (CRM) of active pharmaceutical ingredients (API): metronidazole and captopril. The principal component analysis (PCA) and the hierarchical cluster analysis (HCA) indicated that some results from the homogeneity test were statistically different when the concentrations of all API impurities were considered simultaneously. Through the use of these statistical tools, it was possible to reduce the standard uncertainty due to between-bottle (in)homogeneity (u bb) and consequently the combined standard uncertainty of the certified reference materials (u CRM) with 95% confidence level.
Keywords: Multivariate Analysis; PCA; HCA; Reference standards; Active pharmaceutical ingredients (API)