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Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement (v.17, #6)
Experimental design and data evaluation considerations for comparisons of reference materials by David L. Duewer; Hugo Gasca-Aragon; Katrice A. Lippa; Blaza Toman (pp. 567-588).
The analysis of reference materials (RMs) can help assess the equivalence of chemical measurement processes. When two or more RMs are available for a given measurand, confidently establishing the equivalence of measurement processes requires the RMs to be capable of yielding equivalent results. Evaluating the degrees of equivalence among RMs that differ in analyte quantity and perhaps matrix composition requires an approach other than that used to assess results for samples of a single material. We have more than a decade of experience with an approach that compares the assigned values of RMs to a simple linear model of the relationship between those values and measurement results ideally made under repeatability conditions. In addition to accessing the metrological equivalence of specific RMs, the equivalence of the value-assignment capabilities of the organizations that issue the RMs can also be accessed. This report summarizes our experience with the design of and analysis of studies using this approach and provides numeric and graphical tools for estimating degrees of equivalence. We divide the required tasks into four steps: (1) design, (2) measurement, (3) definition of a reference function, and (4) estimation of degrees of equivalence. We regard the experimental design and measurement tasks as most critical to the eventual utility of the comparison, since creative mathematics cannot fully compensate for poor planning or erratic measurements.
Keywords: Consultative Committee for Amount of Substance—Metrology in Chemistry; Degree of equivalence; Generalized distance regression; Metrological comparability; Metrological equivalence; Reference function; Reference material
Production of three certified reference materials for water content based on mixed solutions of butanol, xylene and propylene carbonate by Haifeng Wang; Kang Ma; Wei Zhang; Ting Huang; Xinhua Dai; Jia Li; Guohua Sun; Hongmei Li (pp. 589-596).
Certified reference materials (CRMs) for water content with good accuracy and homogeneity are required for calibration or validation of the Karl Fischer titration and for establishing the traceability of water content results. Three such CRMs were produced and certified: GBW 13512, 13513 and 13514 are based on solvent mixtures consisting of butanol, xylene and propylene carbonate with water contents of 10.01, 1.067 and 0.139 mg/g, respectively, certified by the Karl Fischer coulometric and volumetric methods. These CRMs were prepared, dispensed and sealed under a humidity equal to the equilibrated humidity of their headspace. In this way, the between-bottle homogeneity uncertainty (u H,rel) could be kept as low as u H,rel = 0.12 % for GBW 13512. The certification methods, that is, Karl Fischer coulometric and volumetric methods, were calibrated using in-house water standards prepared by gravimetry. The results were traceable to the SI unit of mass. The relative deviation of the water contents between the two methods for GBW 13512 was only 0.05 %. The expanded uncertainty (U, k = 2) of three CRMs was 0.12, 0.024 and 0.012 mg/g, respectively. These CRMs for water content with good accuracy can be applied in the calibration or validation of measurement procedures to ensure accurate and comparable results.
Keywords: Certified reference material; Water content; Moisture content; Karl Fischer titration; Traceability; Water activity; Humidity
Alternative calculation of measurement uncertainty with global approach in food microbiology by Emrah Torlak (pp. 597-601).
Calculation of measurement uncertainty is a requirement for all laboratories accredited to ISO/IEC 17025 including those carrying out microbiological analyses. Today, calculation of measurement uncertainty in microbiological analyses using precision data according to global approach principles is widely recognized by the microbiologists due to difficulties in quantification of individual uncertainty sources. In food microbiology, precision data obtained from different samples usually show over-dispersion, and the use of over-dispersed data may result in large variance. The current ISO standard on measurement uncertainty in food microbiology proposes the use of log-transformed precision data to overcome this problem. This paper proposes an alternative procedure to calculate the measurement uncertainty in food microbiology using non-logarithmic precision data. The calculations used in this procedure based on relative range of duplicate analyses can be applied to intra-laboratory reproducibility data obtained from microbiological analyses of which duplicate results show relatively low variation.
Keywords: Measurement uncertainty; Food microbiology; Global approach; Precision
Software support for the Nordtest method of measurement uncertainty evaluation by Teemu Näykki; Atte Virtanen; Ivo Leito (pp. 603-612).
Software support for the Nordtest method of measurement uncertainty evaluation is described. According to the Nordtest approach, the combined measurement uncertainty is broken down into two main components—the within-laboratory reproducibility (intermediate precision) s Rw and the uncertainty due to possible laboratory bias u(bias). Both of these can be conveniently estimated from validation and quality control data, thus significantly reducing the need for performing dedicated experiments for estimating detailed uncertainty contributions and thereby making uncertainty estimation easier for routine laboratories. An additional merit of this uncertainty estimation approach is that it reduces the danger of underestimating the uncertainty, which continues to be a problem at routine laboratories. The described software tool—MUkit (measurement uncertainty kit)—fully reflects the versatility of the Nordtest approach: it enables estimating the uncertainty components from different types of data, and the data can be imported using a variety of means such as different laboratory data systems and a dedicated web service as well as manual input. Prior to the development of the MUkit software, a laboratory survey was carried out to identify the needs of laboratories related to uncertainty estimation and other quality assurance procedures, as well as their needs for a practical tool for the calculation of measurement uncertainty.
Keywords: Measurement uncertainty; Validation; Within-laboratory reproducibility; Bias; Software; Testing laboratories; Quality control; Proficiency testing; Nordtest
The current status and future of medical laboratory quality regulation and accreditation in Ghana by Enoch Cobbina; Julius Yao Agbezudor; Prince Sodoke Amuzu; Thomas K. Gyampomah (pp. 613-619).
High-quality and reliable laboratory services are important components of effective and well-functioning health systems. Accurate, reliable and timely medical laboratory testing is crucial to patient care and disease surveillance. Unfortunately, in many sub-Saharan African countries, medical laboratory systems are adversely affected by the unavailability of medical laboratories, poor laboratory infrastructure and lack of well-trained personnel [1]. Quality in the laboratory is only achieved in a systematic way through the implementation of a quality management system. The results of the study showed that approximately 60 % of the 78 respondents were unaware of the requirements of ISO 15189:2007. A trial of proficiency testing, termed ‘blind proficiency testing’, was carried out in which 19 laboratories determined the concentrations of urea and cholesterol in a proficiency testing material. Of the 19 laboratories that determined the concentration of urea, 63 % produced satisfactory results with scores between −2 and +2. Similarly, 63 % of the participating laboratories obtained satisfactory z scores for cholesterol determination. Some of the laboratories that obtained satisfactory scores for urea determination had unsatisfactory scores for cholesterol determination and vice versa. It is recommended that the Ghanaian government pass a law and establish a standard to regulate medical laboratories in Ghana in order to improve quality in a significant way.
Keywords: Accreditation; Ghana; Medical laboratory; Proficiency testing; Quality regulation; Sub-Saharan Africa
Implementation of a quality management system in a public research centre by Valentina Biasini (pp. 621-626).
In recent decades, it has become increasingly important for public research centres to attract external clients, including government, private and public bodies and companies. They do this by demonstrating their research excellence. A research centre’s ability to provide professional research services can be assessed by competent technical bodies which verify that the research centre’s laboratories operate according to certain predetermined criteria or standards. Although there is no set of generally accepted standards, some regional accreditation bodies already offer accreditation assessment for the R&D laboratories which are in their territory. This article analyses the successful application of a quality management system in a public research centre employing 57 people including researchers, technicians and administrative staff. This system is based on the scheme of regional accreditation of industrial research laboratories which was inspired by ISO 9001:2008 and ISO 17025:2005 and set up by the regional authority. The overall aim of the management system is to monitor all of the industrial research and services which the centre offers to external users, such as government, private and public bodies and companies, and to guarantee that final products, usually technical reports and prototypes, respond to their needs. The accreditation applies to all of the activity of the research centre except for basic research. In this article, the critical factors influencing the success of the implementation of the management system are outlined together with benefits and opportunities. Weak points and problems are analysed, and the actions which were undertaken in order to prevent and manage problems are described.
Keywords: Quality assurance; Research organizations; R&D
From experimental design to quality by design in pharmaceutical legislation by Ivan M. Savic; Valentina D. Marinkovic; Ljiljana Tasic; Dusanka Krajnovic; Ivana M. Savic (pp. 627-633).
Quality by design (QbD) is a concept first outlined by Juran, who believed that quality could be planned and that most quality crises and problems relate to the way in which quality was planned in the first place. Experimental design is a powerful technique and tool for QbD, used for exploring new processes, gaining increased knowledge of the existing processes and optimizing these processes for achieving internationally competitive performance. It is also used for the investigation of relationship between parameters of ill-defined process. In this paper, the experimental design principles in pharmaceutical development and impact of these principles on pharmaceutical legislation have been reviewed. Also, slow implementation of QbD in pharmaceutical industries has been discussed. Pharmaceutical legislation is necessary for companies to continue benefiting from knowledge gained and to continually improve throughout the process lifecycle by making adaptations to assure that root causes of manufacturing problems are quickly corrected.
Keywords: Quality by design; Experimental design; Pharmaceutical quality system; Pharmaceutical legislation
About literature information on functional relationships and limits of detection: may authors improve their statements? by E. Desimoni; B. Brunetti (pp. 635-637).
Attention of experimentalists is called at a proper description of figures of merits when detailing the performances of some electrochemical sensors.
Keywords: Functional relationships; Uncertainties of slope and intercept of regression lines; Linear ranges; Limit of detection approaches
Is “consensus value” a correct term for the product of pooling measurement results?
by Paul De Bièvre (pp. 639-640).