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Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement
[SJR: 0.378] [H-I: 30] [26 followers] Follow

Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0949-1775 - ISSN (Online) 1432-0517
Published by Springer-Verlag

[2351 journals]

Measurements recovery evaluation from the analysis of independent
reference materials: analysis of different samples with native quantity
spiked at different levels
- Authors: Rui M. S. Cordeiro; Constantino M. G. Rosa; Ricardo J. N. Bettencourt da Silva
  Pages: 57 - 71
  Abstract: Measurement uncertainty evaluation involves combining uncertainty components reflecting all relevant random and systematic effects: the precision and trueness uncertainty components, respectively. Typically, trueness is assessed through the analysis of various materials with known reference value, such as certified reference materials (CRMs) or spiked samples, from which it should be decided about the relevance and the need to correct measurement results for systematic effects. Algorithms proposed so far to assess systematic effects are only applicable to the analysis of the same reference material type or assume that some uncertainty components affecting evaluations are negligible or constant. This work presents detailed algorithms for the assessment of systematic effects, through the determination of recovery and the respective recovery uncertainty, applicable to the analysis of various independent reference materials, such as CRMs and spiked samples with native analyte. These algorithms are applicable to cases where native analyte and/or spiking values are associated with relevant and significantly different uncertainties allowing for a reliable assessment of systematic effects and measurement uncertainty for these complex cases. This methodology was successfully applied to the quantification of Na, K, Mg, Ca, Cr, Mn, Fe and Cu in water samples from two proficiency testing schemes, by ICP-OES, where recovery was estimated from the analysis of samples with different native concentrations and spiked at different levels. The relative expanded uncertainties of the measurement results ranged from 28.9 % to 3.9 % and are fit for the monitoring of environmental water samples in accordance with criteria set in the European Union legislation.
  PubDate: 2018-04-01
  DOI: 10.1007/s00769-017-1296-2
  Issue No: Vol. 23, No. 2 (2018)
Measurement uncertainty: requirements set in the accreditation standards
- Authors: Kyriacos C. Tsimillis
  Pages: 109 - 114
  Abstract: Measurement uncertainty is of high importance to all testing and calibration laboratories and those involved in sampling activities. Its evaluation requires good understanding of the method implemented and realisation of all factors contributing to it. It is required that the users of the results fully understand the meaning of uncertainty stated on test reports and calibration certificates and, when needed, ask for clarifications. Laboratories, both the accredited ones and those being prepared towards their accreditation, need to take this into account when evaluating the uncertainty of their results. Competent authorities need to consider the stated uncertainty to compare the result with a legislative limit. The producer can decide on adjustments needed. The consumer may find it more difficult to understand how this “uncertain component” of the results could affect their health, safety or economic rights. This article describes the relevant requirements of the accreditation standards referring both to testing and calibration laboratories and to proficiency testing and reference material producers. Further to this, the article explains why all these factors have to be considered by a laboratory.
  PubDate: 2018-04-01
  DOI: 10.1007/s00769-018-1310-3
  Issue No: Vol. 23, No. 2 (2018)
Occurrence of nitrate in vegetables and dietary exposure assessment for
the Cypriot adolescent consumers
- Authors: Georgios Stavroulakis; Demetris Kafouris; Maria Christofidou; Lefkios Paikousis; Eftychia Christou; Maro Christodoulidou; Popi Kanari; Eleni Ioannou-Kakouri
  Pages: 115 - 122
  Abstract: In this study, a simple, rapid and sensitive ion chromatography method was used for the determination of mass fraction nitrate (mg kg−1) in 396 samples of vegetables. The method performance characteristics were determined after spiking blank samples. The mean recoveries in vegetables ranged from 94.0 % to 108.7 %. Limits of detection and quantification were 10 mg kg−1 and 30 mg kg−1, respectively. The results showed the mass fraction nitrate in vegetables was in the range of 10 mg kg−1–5619 mg kg−1. Leafy, root and stem vegetables, and herbs were the most contaminated, compared to other vegetables. Approximately 87 % of the samples were contaminated with nitrate; however, none of the samples analyzed was above the maximum limits for nitrate in vegetables. The dietary nitrate intake through consumption of vegetables was estimated for the adolescent population in Cyprus. The mean and 95th percentile intake values, based on median nitrate concentrations, were 1.12 kg d−1 and 3.42 mg kg−1 d−1, respectively. A small percentage (3.3 %) of the adolescent population had a nitrate intake above the Acceptable Daily Intake (3.7 mg kg−1 d−1). Lettuce and other leafy vegetables (spinach, rucola, purslane, beet leaves) contributed nearly 60 % to the overall nitrate exposure (mg kg−1 d−1).
  PubDate: 2018-04-01
  DOI: 10.1007/s00769-018-1311-2
  Issue No: Vol. 23, No. 2 (2018)
Congresses, conferences, workshops and courses
- Pages: 123 - 123
  PubDate: 2018-04-01
  DOI: 10.1007/s00769-018-1314-z
  Issue No: Vol. 23, No. 2 (2018)
Classification of objects into quality categories in the presence of
hierarchical decision-making agents
- Authors: Fiorenzo Franceschini; Domenico Maisano
  Pages: 5 - 17
  Abstract: In many practical contexts, it is often required to classify some objects of interest into predetermined unordered quality categories. This operation—referred to as quality classification problem—has received considerable attention in many fields of research, such as Analytical Chemistry, Materials Science, Medicine, Manufacturing, Quality Engineering/Management, Decision Analysis. Assuming that multiple agents perform subjective assignments of categories to the objects of interest, a further problem is that of fusing these assignments into global classifications. To this purpose, the mode and the weighted mode are very practical measures, as long as agents are equi-important or their (different) importance is expressed in the form of a set of weights. Unfortunately, these measures are not appropriate for quality classification problems where the agents’ importance is expressed in the form of a rank ordering (hierarchy). The aim of this article is to present a new method, which addresses the latter quality classification problem in a relatively simple and practical way. The peculiarity of this method is that the different importance of agents determines a different priority in considering their assignments and not a different weight of these assignments. A detailed description of the new method is supported by a realistic example in the Analytical Chemistry field.
  PubDate: 2018-02-01
  DOI: 10.1007/s00769-017-1291-7
  Issue No: Vol. 23, No. 1 (2018)
Certification for trace elements and methyl mercury mass fractions in
IAEA-456 marine sediment sample
- Authors: Emilia Vassileva; Sabine Azemard; Petko Mandjukov
  Pages: 29 - 37
  Abstract: Marine sediment certified reference material (CRM), IAEA-456 was recently produced by the Environment Laboratories of the International Atomic Energy Agency (IAEA) and certified for trace elements and methyl mercury (CH3Hg). This paper presents the sample preparation methodology, material homogeneity and stability studies, evaluation of results from the characterisation campaign, the assignment of property values and their associated uncertainty. The reference values and associated expanded uncertainty for nine trace elements (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn) and CH3Hg in marine sediment sample are established. The new CRM can be used for the development and validation of analytical methods, for the determination of trace elements and methyl mercury in sediments and also for quality assurance/quality control purposes.
  PubDate: 2018-02-01
  DOI: 10.1007/s00769-017-1297-1
  Issue No: Vol. 23, No. 1 (2018)
Preparation and characterization of phosphate rock as quality control
material
- Authors: Caroline Santos da Silva; Gilberto Batista de Souza; Ana Rita Araujo Nogueira
  Pages: 39 - 45
  Abstract: A quality control material for inorganic constituents present in a phosphate-bearing rock used to manufacture phosphate fertilizers was produced and characterized according to the ISO Guide 80. The evaluation of the estimated minimum mass, homogeneity, and stability of the material was performed using microwave-assisted digestion and inductively coupled plasma optical emission spectrometry (ICP-OES) as an in-house validated technique for determination of Al, As, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, V, and Zn. Phosphorus mass fraction determination was done by laser-induced breakdown spectroscopy. The accuracy of the measurement results was confirmed by analyzing the certified phosphate rock and fertilizer certified reference materials according to NIST SRM 694 and SRM 695. One-way analysis of variance (ANOVA) was applied to the measurement data, and the homogeneity and stability of the material presented averages within the 95 % confidence interval. The results from the preparation and with collaborative trial allowed the calculation and estimation of the consensus value and its expanded measurement uncertainties, obtained by combining the uncertainty contributions from characterization (u char), between-bottle homogeneity (u bb), short-term stability (u sts), and long-term stability (u lts) for each evaluated analyte mass fraction.
  PubDate: 2018-02-01
  DOI: 10.1007/s00769-017-1295-3
  Issue No: Vol. 23, No. 1 (2018)
Principles for the assessment of homogeneity and stability in the new ISO
Guide 35:2017
- Authors: Stephen L. R. Ellison; Angelique Botha
  Pages: 47 - 51
  Abstract: The production of reference materials (RMs) is a key activity for the improvement and maintenance of a worldwide coherent measurement system. General requirements for all types of RM production are set out in ISO 17034. These general requirements include the assessment of homogeneity and stability. Technical detail is, however, left entirely to other guides, of which ISO Guide 35 is the most general and comprehensive. This paper provides an overview of the provisions for stability and homogeneity assessment in ISO Guide 35:2017, with particular attention to changes from the 2006 edition. Important changes include new guidance on the need for experimental studies when substantial prior experience is available; a larger range of homogeneity study designs; improved guidance on the use of accelerated stability studies; additional, and more flexible, guidance on within-unit homogeneity assessment; greater attention to post-certification monitoring; and new provisions for end-user storage and repeated sampling from individual RM units.
  PubDate: 2018-02-01
  DOI: 10.1007/s00769-017-1293-5
  Issue No: Vol. 23, No. 1 (2018)
Report on the 40th meeting of ISO/REMCO
- Authors: Angelique Botha; John Hammond; Hendrik Emons; Stéphane Sauvage
  Abstract: The 40th meeting of the Reference Material Committee of ISO, ISO/REMCO, was held in Berlin, Germany, from 26 to 29 June 2017, and was hosted by the Federal Institute for Materials Research and Testing (BAM) and the German Institute for Standardization (DIN). This report details and summarizes the discussions and findings of the associated group sessions, and meetings.
  PubDate: 2018-04-03
  DOI: 10.1007/s00769-018-1313-0
Definition of reference values in synthetic emission monitoring bench
loops
- Authors: D. Cipriano; L. Fialdini
  Abstract: Proficiency tests (PTs) are widely used in order to certify capabilities of laboratories, determine and validate uncertainties and validate methods. One of the major difficulties in emission monitoring PTs is due to realisation of a stable and ‘metrological correct’ gas matrix, and, since now, the most common approach is based on emissions gases taken from industrial boilers, from which, therefore, the composition is ‘metrological’ unknown, or on ambient air added with compounds of interest, but, in this case, the chemical behaviour of the matrix may be different from real cases. Synthetic emissions loops give the possibility to fill this gap, but require particular protocols for definition of reference values and their uncertainties. One solution, adopted on the facility realised at RSE research centre in Italy, is shown.
  PubDate: 2018-03-27
  DOI: 10.1007/s00769-018-1312-1
Discussion on homogeneity assessment of reference materials based on
uncertainty comparison method
- Authors: Chonghua Liu; Zhiyong Ding; Yong Tian; Lezhou Yi; Ningshan Huang
  Abstract: An uncertainty comparison method is proposed to assess the homogeneity of reference materials. The method compares “standard uncertainty associated with between-unit variability” (ubb) with “target standard uncertainty” (utrg) or “measurement uncertainty” (umeas) to solve the problems in assessing homogeneity of reference materials. Methods for the calculation of ubb, utrg and umeas as well as criterion for the quantitative judgment of sample homogeneity are introduced. When ubb ≤ 0.3utrg, it shows the sample is considered to be homogeneous; when 0.3utrg < ubb ≤ 0.7utrg, the sample is considered to be sufficiently homogeneous for the intended use; and when ubb > 0.7utrg, the sample is considered to be inhomogeneous. The uncertainty comparison method is compared with the F test method and shown to be more objective for the assessment of the homogeneity of certified reference materials for the chemical testing of toys.
  PubDate: 2018-02-02
  DOI: 10.1007/s00769-017-1308-2
Congresses, conferences, workshops and courses
- PubDate: 2018-02-01
  DOI: 10.1007/s00769-018-1309-9
New Editor-in-Chief
- Authors: Adriaan M. H. van der Veen
  PubDate: 2018-01-16
  DOI: 10.1007/s00769-017-1306-4
New challenges
- Authors: Ales Fajgelj
  PubDate: 2018-01-09
  DOI: 10.1007/s00769-017-1307-3
Trueness verification survey for blood lead concentration measurement in
Chinese clinical laboratories
- Authors: Shuai Yuan; Wei Wang; Jianping Li; Mingxia Liu; Junwei Xin; Fa L. He; Kun Zhong; Zhi G. Wang
  Abstract: The results of trueness verification for blood lead measurement were analyzed in a 2016 nationwide external quality assessment (EQA) survey, in order to evaluate current approaches of blood lead measurement in Chinese Laboratories and their traceability to certified reference materials (CRMs). A panel of 2 frozen whole blood CRMs with values assigned by an absolute quantitative method was provided to 12 laboratories with satisfactory performances from the 2015 blood lead EQA scheme. Participants were required to measure the samples 5 times each day for 3 consecutive days and report all 15 data, which were then calculated for means and standard deviations. Data were statistically analyzed by adopted method groups, before comparing with the assigned values to assess the trueness of blood lead measurement using different approaches. Eleven laboratories reported on schedule, rendering a reporting rate of 91.7 %. The target values for the two batches were (37.6 ± 2.7) μg/L and (124.6 ± 4.5) μg/L, respectively. By the evaluation criterion of target value ± 20 µg/L, the pass rates were 72.7 % for the lower concentration and 54.5 % for the higher concentration, while 5 out of 11 laboratories delivered satisfactory results for both CRMs. The overall performance of the few participating laboratories in this EQA survey was basically acceptable by CLSI standard on the whole, yet barely desirable for the higher concentration. Therefore, trueness verification of blood lead measurement with CRMs is potentially necessary for national EQA schemes, which can be imperative as part of the validation procedures of analytical methods in clinical settings.
  PubDate: 2017-12-20
  DOI: 10.1007/s00769-017-1304-6
Correction to: Combined uncertainty factor for sampling and analysis
- Authors: Michael H. Ramsey; Stephen L. R. Ellison
  Abstract: In the penultimate paragraph of the original publication, a confidence interval of 93 mg/kg to 971 mg/kg was reported. These values should be 114.5 mg/kg to 786.2 mg/kg.
  PubDate: 2017-12-18
  DOI: 10.1007/s00769-017-1305-5
Optimizing measurement uncertainty to reduce the risk and cost in the
process of conformity assessment
- Authors: M. Dastmardi; M. Mohammadi; B. Naderi
  Abstract: Uncertainty in measurement is very important in the process of conformity assessment. As it is generally declared, based on the measured value of a property of an item, there is always the risk of incorrect decisions, which are of two types: an item accepted as “conforming” may actually be “non-conforming”, and an item rejected as “non-conforming” may actually be “conforming”. In order to reduce the risks associated with decision-making, it is required to reduce the measurement uncertainty to an acceptable level termed as “target uncertainty”. In order to reduce the uncertainty of a particular measurement, it would be necessary to focus on decreasing the uncertainties arising from the relevant components. There are always different solutions to reduce the uncertainties arising from each inclusive component. Each of these solutions imposes a different cost on the measurement system. Therefore, a solution should be selected, among several possible alternatives, to reduce the uncertainties arising from each relevant component and to impose the lowest cost to the measurement system to “target uncertainty”. Accordingly, in this paper through a case study, a model is presented that can reduce uncertainty with the lowest possible cost to the optimally needed level using a mathematical optimization technique. The mathematical model presented in this paper can be used in measurement uncertainty optimization in many laboratories, which require a reduction in uncertainty and the risks associated with decision-making based on measurement results. Furthermore, the use of the proposed model will help to reduce the unnecessary costs of analysis in different laboratory centers.
  PubDate: 2017-12-08
  DOI: 10.1007/s00769-017-1294-4
Quality system implementation in the National Metrology Institute of
Montenegro
- Authors: Vanja Asanovic; Milena Raonic; Naina Cuturic-Knezevic; Goran Vukoslavovic; Milena Popovic; Vladan Jestrovic
  Abstract: Accreditation of calibration laboratories is a means for achieving competence recognition and assuring customers that their calibration services are accurate and reliable. Moreover, it is a powerful tool for a National Metrology Institute (NMI), enabling the formal acceptance of its measurement results. It could be especially useful when calibration activities are performed in well-developed laboratories, which have participated successfully in interlaboratory comparisons but have been awaiting the publication of Calibration and Measurement Capabilities in the BIPM Key comparison database. This paper describes establishment and implementation of a quality management system in the NMI of Montenegro called Bureau of Metrology (MBM) that complies with ISO/IEC 17025. We have presented the results of the first audit evaluation, corrective actions, preparation of quality management documentation, measurement traceability, as well as advantages of being accredited. Our experience of implementing ISO/IEC 17025 for the accreditation of national calibration laboratories established within the MBM shows that strategic planning, establishment of long-term objectives, as well as the commitment to fulfilling standard requirements are the basis for acceptable calibration results. International acceptance of confidence and reliability of calibration services and measurement results provided by the MBM laboratories represents a useful marketing tool for promoting the image of the institution.
  PubDate: 2017-12-04
  DOI: 10.1007/s00769-017-1303-7
The hitherto non-included component in the uncertainty budget for
gravimetric measurement of particulate matter concentration in a conduit
- Authors: Przemysław Kateusz
  Abstract: This article discusses the accuracy of the gravimetric measurement method of total particulate matter concentration in waste gases where the basic assumption is that sample collection of dust-laden gas is done in a grid with a finite number of points in the conduit’s measurement plane. In this standard approach, the sample is assumed to be representative for dust-laden gas in the conduit, and consequently, the total particulate matter concentration measured for the sample is considered the mean concentration in the conduit. The article investigates this assumption against the standard-imposed number of sampling points and in view of spatial distributions of particulate matter concentration in industrial plants which—being continuous—are not identified in measuring practice. Possible distributions were simulated both for particulate matter concentration and for gas velocity in rectangular conduits, and the following were calculated: (a) an accurate mean particulate matter concentration in the measurement plane, based on its definition employing continuous distributions of particulate matter concentration and gas velocity and (b) the concentration in a sample, i.e. measured concentration. Measurement deviation between those concentrations was determined, which is specific for cumulative gas sampling. Using the obtained set of possible deviations, an estimation method was suggested for the relevant uncertainty component of the gravimetric method, which so far has not been taken into account in the industrial measurement accuracy analyses. It turns out that the level of this uncertainty component for measuring the mean particulate matter concentration in the conduit (resulting from “measurement discretization”) is not to be ignored.
  PubDate: 2017-12-04
  DOI: 10.1007/s00769-017-1302-8
Correction to: Uncertainty estimation of the determination of chemical sum
parameters in water
- Authors: Tony Venelinov
  Abstract: Unfortunately, Eq. 3 was incorrectly presented in the original publication.
  PubDate: 2017-10-10
  DOI: 10.1007/s00769-017-1290-8