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Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement (v.15, #11)
The impact of sampling on variance functions in analytical chemistry and microbiology by Peter Lischer (pp. 603-611).
This manuscript provides evidence that meaningful estimates of uncertainty can be obtained from laboratory-performance studies on condition that a log-linear relationship holds between concentration level and standard deviation of the measurement results. In such cases, the more expensive interlaboratory method-performance studies can be avoided. Some theoretical background is given and demonstrated with two examples. In particular, it is emphasized that variance functions are affected both by sampling and by analytical errors. An estimate of the proportion of the uncertainty due to sample heterogeneity in interlaboratory trials is provided by dint of Pierre Gy’s sampling theory. A stable ratio between ‘sampling’ and ‘analytical’ variance corresponds to a log-linear variance function and vice versa.
Keywords: Pierre Gy’s sampling theory; Log-linear variance function; Generalized Horwitz ratio; Quantifying uncertainty; Qualifying laboratories
Certification of the mass fractions of trace elements and pentachlorophenol in an impregnated wood reference material by Holger Scharf; Roland Becker; Wolfram Bremser; Hans-Gerhard Buge; Detlef Lück (pp. 613-619).
The resource-saving utilisation of recovered waste wood is a matter of growing concern. In several European countries, this utilisation is governed by regulations and is dependent on the contents of certain trace elements and organic compounds. Thus, for decision-making with respect to waste wood management (recycling or combustion), reliable analytical data are needed and, due to their great economic and environmental impact, must be assured by appropriate quality control. To support the improvement in quality assurance in waste wood analysis, for the first time, a wood reference material was certified for its mass fractions of arsenic, cadmium, chromium, copper, lead, mercury, and pentachlorophenol (PCP). These analytes were selected because they represent typical constituents of wood preservatives most widely used in the past. Material preparation and testing of homogeneity and stability were carried out by BAM Federal Institute for Materials Research and Testing. The certification measurements were performed involving selected laboratories with documented expertise in the field of waste wood analysis. The certified values and their corresponding uncertainties were assigned in full compliance with the requirements of ISO Guide 35. The certified mass fractions and their expanded uncertainties (k = 2) are as follows: (3.1 ± 0.5) mg/kg for As, (3.02 ± 0.24) mg/kg for Cd, (36.4 ± 2.6) mg/kg for Cr, (22.9 ± 1.7) mg/kg for Cu, (0.60 ± 0.14) mg/kg for Hg, (39 ± 4) mg/kg for Pb, and (7.9 ± 0.6) mg/kg for PCP. The certified material is available as European Reference Material ERM®-CD100.
Keywords: Waste wood; Trace elements; Pentachlorophenol; Certification; European Reference Material
Toward standardization of quality assessment in laboratory medicine by using the same matrix samples for both internal and external quality assessments by Ibrahim Unsal; Abdurrahman Coskun; Mustafa Serteser; Tamer C. Inal; Aysel Ozpinar (pp. 621-627).
The main purpose of quality assurance procedures in clinical laboratories is to ensure that test results are appropriate to maintain excellence in the diagnosis, monitoring, and treatment of disease. However, in current practice, no standardized procedure or frequency for the evaluation of methods exists, particularly in external quality assessment. Furthermore, different quality control materials are typically used for internal and external quality assessment. To overcome these discrepancies, we used samples with the same matrix for both internal and external quality assessments of a group test performed in our laboratory. We then calculated total error using real bias (target value obtained by reference method) and the imprecision of each test and compared our results with the total error allowable, derived from biological variation data. We suggest that the strategy of using the same matrix samples for both internal and external quality assessment is cost-effective, can be readily used by staff, and will facilitate the standardization of quality control in clinical laboratories.
Keywords: External quality; Biological variation; Quality control; Bias; Total allowable error; Laboratory standardization
Measuring the performance of quality assurance processes: pharmaceutical industry deviation management case study by Zorana Boltic; Nenad Ruzic; Mica Jovanovic; Slobodan Petrovic (pp. 629-636).
This article presents experience from the practice of a successful pharmaceutical company related to design and implementation of performance measures (PMs) for deviation management linked to the analysis of impact on the production cost for the selected product. Case study focuses on PMs within good manufacturing practice (GMP) processes related to quality assurance (QA) and quality management, with the aim of complying with its future requirements proposed by the European Commission. Critical areas were identified based on data gathered from the industrial deviation database. Implementation of the suggested corrective actions showed significant improvement in terms of reducing their number for more than 50% per selected deviation category. The results obtained in the course of this practice-oriented study contribute to further improvement of deviation management in the pharmaceutical industry and performance measurement of other GMP processes. The suggested performance measurement concept and problem-solving techniques may serve both practitioners and the decision-makers within QA and quality control (QC) in order to improve their processes by implementing relevant regulatory requirements for quality management and maintain compliance.
Keywords: GMP; Deviation management; Performance measures; Quality assurance; Quality management
Fuzzy logic-based procedures for GMO analysis by Gianni Bellocchi; Christian Savini; Marc Van den Bulcke; Marco Mazzara; Guy Van den Eede (pp. 637-641).
Key to sound validation studies is the formalization and harmonization of procedures for design of experiment and interpretation of results. International guidelines (ISO 5725, ENGL) are available for the validation of GMO detection methods, and ad-hoc validation statistics (e.g. per cent bias, repeatability and reproducibility) are used for in-house and inter-laboratory testing and decision-making. Acceptability criteria have been set but not every situation can be covered by a preset rule; the interpretation of results in validation largely depends on expert judgement being a matter of professional judgment and expertise. Fuzzy logic-based techniques may be used to summarize the information obtained by independent validation statistics and are helpful in such respect. A comprehensive indicator of method performance permits direct comparison between methods and facilitates the evaluation of multiple, yet contradictory statistics. The European Union Reference Laboratory for GM Food and Feed has already proposed the fuzzy principle in the context of method validation. Other studies have also proved its applicability in other areas of GMO analysis, but the application has been limited hitherto. In this article, we review the fuzzy logic principle and its potential to support the continuous progress of GMO science and routine laboratory analyses.
Keywords: Fuzzy logic; Genetically modified organisms; Real time quantitative polymerase chain reaction (qPCR); Validation of methods
Metrological compatibility—a key issue in future accreditation by Kaj Heydorn (pp. 643-645).
Global acceptance of measurement results from accredited laboratories is linked to their metrological compatibility, defined in VIM 3 as a comparison between all measurement results in a set. It is therefore most unfortunate that a recent IUPAC/CITAC Guide applies the same term to a comparison between a certified value and the measured quantity values in a set.
Keywords: Metrological compatibility; Proficiency testing; T-statistic; Mutual Recognition; IUPAC
The third edition of ISO Guide 34: what were the drivers for the revision and what is new? by Andrée Lamberty; Hendrik Emons (pp. 647-652).
After the International Laboratory Accreditation Cooperation (ILAC) had taken in 2004, the resolution to conduct accreditation of producers of reference materials according to ISO Guide 34 ‘General requirements for the competence of reference material producers’ in combination with ISO/IEC 17025 ‘General requirements for the competence of testing and calibration laboratories’, ISO/REMCO, the ISO Committee on Reference Materials, decided in 2005 to revise ISO Guide 34 to align it closer with ISO/IEC 17025 and to clarify certain issues for accreditors and producers seeking accreditation without adding new requirements. Moreover, the publication in 2007 of ISO/IEC Guide 99 ‘International vocabulary of metrology—Basic and general concepts and associated terms (VIM)’ triggered additional adaptations of the guide.
Keywords: Accreditation; Reference material producer; Revision ISO Guide 34; ISO/REMCO
Erratum to: Laboratory effects models for interlaboratory comparisons
by Blaza Toman; Antonio Possolo (pp. 653-654).