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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  [2352 journals]
• Full method validation in clinical chemistry
• Authors: Elvar Theodorsson; Bertil Magnusson
Pages: 235 - 246
Abstract: Clinical chemistry is subject to the same principles and standards used in all branches of metrology in chemistry for validation of measurement methods. The use of measuring systems in clinical chemistry is, however, of exceptionally high volume, diverse and involves many laboratories and systems. Samples for measuring the same measurand from a certain patient are likely to encounter several measuring systems over time in the process of diagnosis and treatment of his/her diseases. Several challenges regarding method validation across several laboratories are therefore evident, but rarely addressed in current standards and accreditation practices. The purpose of this is paper to address some of these challenges, making a case that appropriate conventional method validation performed by the manufacturers fulfils only a part of the investigation needed to show that they are fit for purpose in different healthcare circumstances. Method validation across several laboratories using verified commercially available measuring systems can only be performed by the laboratories—users themselves in their own circumstances, and need to be emphasised more by the laboratories themselves and accreditation authorities alike.
PubDate: 2017-10-01
DOI: 10.1007/s00769-017-1275-7
Issue No: Vol. 22, No. 5 (2017)

• Method validation in analytical sciences: discussions on current practice
and future challenges
• Authors: Vicki Barwick; Stephen L. R. Ellison; Elin Gjengedal; Bertil Magnusson; Olivier Molinier; Marina Patriarca; Lorens Sibbesen; Nicole Vanlaethem; Isabelle Vercruysse
Pages: 253 - 263
Abstract: Eurachem held a workshop on method validation in analytical sciences in Gent, Belgium, on 9–10 May 2016. A summary of the working group discussions is provided here. The discussions covered a range of issues concerned with current practice and future challenges in method validation, i.e. setting requirements for a method to be validated; planning validation studies; validation of qualitative and semi-quantitative methods; validation of multi-parameter methods; determination of trueness/bias; assessment of working range; validation in microbiology; and method validation under flexible scope of accreditation. Delegates (129) from 24 different countries and from different backgrounds, e.g. from both public and private laboratories, laboratory associations, accreditation bodies and universities, attended the working groups, thus providing opportunities to collect a variety of views and experiences as well as to identify potential gaps in current guidance and regulations. While the practicalities of assessing method performance characteristics are generally well understood, the issue of setting requirements for those characteristics beforehand is less straightforward. Although a number of documents addressing the principles of method validation are available, guidance on dealing with more complex and ‘non-ideal’ situations, as well as examples of good practice, would be welcomed and greater harmonisation of approaches was deemed necessary. There remains a need for guidance on both the concepts that apply to ‘qualitative’ or ‘nominal’ test methods and on the practical implementation of validation studies in such cases.
PubDate: 2017-10-01
DOI: 10.1007/s00769-017-1286-4
Issue No: Vol. 22, No. 5 (2017)

• Change of shift
• PubDate: 2017-11-10
DOI: 10.1007/s00769-017-1301-9

• Farewell
• Authors: H. Emons
PubDate: 2017-11-10
DOI: 10.1007/s00769-017-1300-x

• Certification for trace elements and methyl mercury mass fractions in
IAEA-456 marine sediment sample
• Authors: Emilia Vassileva; Sabine Azemard; Petko Mandjukov
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: 2017-11-04
DOI: 10.1007/s00769-017-1297-1

• Congress, conferences, workshops and courses
• PubDate: 2017-11-02
DOI: 10.1007/s00769-017-1299-z

• Bayesian analysis of homogeneity studies in the production of reference
materials
• Authors: Adriaan M. H. van der Veen
Abstract: For almost two decades, the batch homogeneity in the production of reference materials has been evaluated using analysis of variance (ANOVA) to determine the between-bottle standard deviation. This approach replaced at that time the use of the F-test in ANOVA to determine whether the ratio of the mean squares $${MS}_{\mathrm {between}}/{MS}_{\mathrm {within}}$$ is statistically significant. Problems arise when $${MS}_{\mathrm {between}} < {MS}_{\mathrm {within}}$$ , because classical ANOVA provides a negative between-bottle variance, which is then often set to zero. By using a Bayesian hierarchical model, based on the same assumptions as traditional ANOVA, we show that even if $${MS}_{\mathrm {between}} < {MS}_{\mathrm {within}}$$ , there can be a relevant level of between-bottle inhomogeneity to account for. The Bayesian analysis produces a nonzero value for the between-bottle standard deviation, which dismisses the practice of setting this standard deviation to 0. At the same time, it dismisses the current guidance given in ISO Guide 35 under these circumstances. Finally, it is shown that traditional ANOVA, meta-analysis methods and Bayesian analysis give very similar answers as long as $${MS}_{\mathrm {between}} > {MS}_{\mathrm {within}}$$ , so there is no need to discourage using these methods in favour of a Bayesian analysis, provided that the repeatability of the measurement method used to conduct the between-bottle homogeneity study is sufficient to characterise the dispersion across the bottles (items) in a batch of a reference material.
PubDate: 2017-11-02
DOI: 10.1007/s00769-017-1292-6

• Preparation and characterization of phosphate rock as quality control
material
• Authors: Caroline Santos da Silva; Gilberto Batista de Souza; Ana Rita Araujo Nogueira
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: 2017-11-01
DOI: 10.1007/s00769-017-1295-3

• Principles for the assessment of homogeneity and stability in the new ISO
Guide 35:2017
• Authors: Stephen L. R. Ellison; Angelique Botha
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: 2017-10-25
DOI: 10.1007/s00769-017-1293-5

• Laboratory capacity building through the use of metrologically traceable
reference values in proficiency testing programmes
• Authors: Robert Kaarls; Lindsey Mackay; Angela Samuel; Della Wai-mei Sin; Chuen-shing Mok; Yee-lok Wong; Yiu-chung Yip
Abstract: There is an increasing need for laboratory capacity building through the organisation of proficiency testing programmes with metrologically traceable reference values in the Asia-Pacific region. Stakeholders such as the regional metrology organisation, metrology institutes, and accreditation bodies are increasingly aware that consensus values of proficiency testing programmes could sometimes be significantly biased if the participating laboratories do not have clear understanding of their measurement capabilities and measurement uncertainties. In this article, we provide a review of the effectiveness of the use of reference values obtained from international comparisons among metrology institutes for performance evaluation in associated proficiency testing programmes. Important issues are discussed including determination of assigned values, the main methods employed by national metrology institutes/designated institutes and field analytical laboratories for analysis, estimation of measurement uncertainty, and guidance on analytical challenges presented by these studies. Application of measures such as appropriate matrix reference materials, particularly from incurred sources, for assessing extraction efficiencies and other measurement procedural issues, and proper knowledge of the uncertainty budgets are essential tools leading to effective and reliable measurements.
PubDate: 2017-10-25
DOI: 10.1007/s00769-017-1298-0

• 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

• Classification of objects into quality categories in the presence of
hierarchical decision-making agents
• Authors: Fiorenzo Franceschini; Domenico Maisano
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: 2017-10-07
DOI: 10.1007/s00769-017-1291-7

• The new International Standard ISO 17034: general requirements for the
competence of reference material producers
• Authors: Stefanie Trapmann; Angelique Botha; Thomas P. J. Linsinger; Sean Mac Curtain; Hendrik Emons
Abstract: The International Organization for Standardization (ISO) has published ISO 17034:2016 on the general requirements for the competence of reference material producers (RMPs). Previously, these requirements were addressed in ISO Guide 34:2009, originally developed by the ISO Committee on Reference Materials (ISO/REMCO). The need for an International Standard was triggered as several accreditation bodies could not accredit to a guide, at all, while in other countries ISO Guide 34 could only serve as accreditation standard in combination with ISO/IEC 17025. For the transformation into a conformity assessment standard of the ISO/IEC 17000 series, the ISO Committee on Conformity assessment (ISO/CASCO) and ISO/REMCO joined forces. A Joint Working Group, formed by experts and stakeholders from both committees, finalised the transformation within 2 years. During the transformation, the structure of ISO 17034 has been aligned with other ISO/IEC 17000 series standards and the content of ISO 17034 has been harmonised with the recent editions of other relevant ISO Guides. Requirements for the production of reference materials (RMs) were elaborated on more clearly in the new standard, specifying the requirements for (non-certified) reference materials and the additional requirements for certified reference materials. The new International Standard ISO 17034:2016 supersedes ISO Guide 34:2009.
PubDate: 2017-09-26
DOI: 10.1007/s00769-017-1285-5

• Congress, conferences, workshops and courses
• PubDate: 2017-09-06
DOI: 10.1007/s00769-017-1289-1

• Are the present measurement standards still valid after SI
redefinition'
• Authors: Franco Pavese
Abstract: The SI revision potentially places some basic concerns to all users, one being the validity of their present standards under the new definition. The paper compares what is spelled out in the new SI Brochure draft to what should be specified for practical implementation. The result of the analysis is uncertain for some level of implementation and some standards, with, on the other hand, some positive aspects also illustrated in the paper, not always found explicit in the formal texts.
PubDate: 2017-08-16
DOI: 10.1007/s00769-017-1282-8

• Method validation for determination of amino acids in feed by UPLC
• Authors: Katarzyna Szkudzińska; Ilona Smutniak; Jolanta Rubaj; Waldemar Korol; Grażyna Bielecka
Abstract: The paper presents results of validation of an analytical procedure based on ultra-performance liquid chromatography technique (UPLC) for determination of 17 amino acids in different feeds. The following performance characteristics were determined for the investigated feeds: relative standard deviations of repeatability and intermediate precisions ranged from 0.4 % to 4.6 %, and from 0.8 % to 7.9 %, respectively; recovery rates ranged from 87 % to 104 %, and limit of detection was from 0.06 g kg−1 (methionine) to 0.72 g kg−1 (glutamic acid). Two approaches were used to estimate measurement uncertainty giving values in a range of 5.1 % to 5.5 %. These performance characteristics are in agreement with the values reported in Commission Regulation (EU) No 152/2009 for the ion exchange chromatography with spectrophotometric detection.
PubDate: 2017-08-01
DOI: 10.1007/s00769-017-1281-9

• Development of primary standard gas mixtures containing 10 µmol/mol
oxygen in nitrogen with verification by a two-oven GC-TCD system for
effective separation of oxygen from argon in presence of plenty of
nitrogen
• Authors: Takuya Shimosaka
Abstract: Primary standard gas mixtures (PSMs) containing 10 µmol/mol oxygen in nitrogen were prepared in aluminum alloy cylinders from pure nitrogen and oxygen gases according to ISO 6142-1. We developed a system consisting of a gas chromatograph with a thermal conductivity detector (GC-TCD) and two ovens to verify precisely the amount-of-substance fraction of oxygen in the PSMs at a level of 10 µmol/mol. As pure nitrogen gas usually contains argon as an impurity, it is necessary to separate the oxygen peak from the argon peak in order to verify the amount-of-substance fraction of oxygen in the PSMs. Although the use of packed columns is essential in order to achieve high precision using a GC-TCD system, it is notoriously difficult to separate oxygen and argon by this method. To overcome this problem, we used two gas chromatograph ovens: The first oven separates oxygen and argon from the nitrogen, whereas the second oven—held at −15 °C or below—separates oxygen and argon. The two-oven GC-TCD system was able to achieve good resolution between the oxygen and argon peaks. The relative uncertainty in the determination of the oxygen fraction obtained using this system was 0.35 %. In order to avoid adsorption of oxygen onto the inner surface of the aluminum cylinder, we pretreated each cylinder by filling it with a standard gas mixture of oxygen in nitrogen at an oxygen partial pressure similar to that of the PSMs. The cylinders were then evacuated and used for the preparation of the target PSMs. From long-term monitoring using the GC-TCD system, we found the PSMs containing 10 µmol/mol oxygen in nitrogen to be stable for at least 30 months. The expanded combined uncertainties for the PSMs (k = 2) were found to be 0.026 µmol/mol to 0.036 µmol/mol, according to ISO 6142-1.
PubDate: 2017-07-21
DOI: 10.1007/s00769-017-1279-3

• G. Férard, R. Dybkaer and X. Fuentes-Arderiu: Compendium of terminology
and nomenclature of properties in clinical laboratory sciences,
recommendations 2016 (Silver Book, 2nd ed.)
• Authors: David B. Hibbert
PubDate: 2017-07-12
DOI: 10.1007/s00769-017-1277-5

• Uncertainty evaluation for the determination of the dissolved fraction of
sulpiride content in tablets
• Authors: Biying Du
Abstract: The aim of this work was to establish a mathematical model to identify the main source of measurement uncertainty, quantify each uncertainty component, and calculate the combined and expanded uncertainties for determination of the fraction of sulpiride dissolved from tablets by UV spectrophotometry. The uncertainties on the absorbance (sample and standard), volumetric flasks and volumetric pipettes have important influence on the overall uncertainty. The average sulpiride fraction released from six tablets was 75.5 %, with an expanded uncertainty of 3.7 % (k = 2). Uncertainty is a relevant tool in assessment of compliance or non-compliance of in-process and final pharmaceutical products. Evaluation of the uncertainty of the dissolution measurement contributes to scientific explanation and interpretation of testing data, and ensures the results to be more accurate, impartial and convincing when testing a sample against specification or legislation.
PubDate: 2017-06-29
DOI: 10.1007/s00769-017-1273-9

• A statistical procedure for the assessment of bias in analytical methods
using conditional probabilities
• Authors: Robert B. Frenkel; Ian Farrance
Abstract: A new approach is described for the simultaneous treatment of bias and imprecision in clinical chemistry. The approach makes use of the general law of conditional probabilities. The result is a density distribution of the measurand that incorporates both imprecision and bias and avoids the contentious linear combination of these quantities as a ‘total error’. This leads naturally to a figure-of-merit in proficiency testing or method comparison that has intuitive visual appeal. We also discuss an established figure-of-merit in proficiency testing, namely the E n number.
PubDate: 2017-06-29
DOI: 10.1007/s00769-017-1274-8

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