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Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement (v.16, #6)


Practical aspects concerning validation and quality control for forensic and clinical bioanalytical quantitative methods by Sarah M. R. Wille; Frank T. Peters; Vincent Di Fazio; Nele Samyn (pp. 279-292).
Reporting reliable analytical data is the backbone of forensic and clinical bioanalytical research and applications. Therefore, international agreement concerning validation and quality control requirements is needed. Several international guidelines provide a standard for fundamental validation parameters such as selectivity, matrix effects, method limits, calibration, accuracy, precision and stability. However, it is not always easy for the analyst to ‘translate’ these guidelines into practice. International guidelines remain nonbinding protocols that need to be updated according to the type of application and the analyst’s method requirements and depends on the evolution of analytical techniques. In this publication, suggestions for experimental set-up, statistical approaches and straightforward acceptance criteria for validation of forensic bioanalytical applications are suggested. Furthermore, permanent quality control, to ensure state-of-the-art quantitative analytical performances, as well as measurement uncertainty influencing interpretation is discussed.

Keywords: Experimental set-up; Acceptance criteria; Validation; Quality control; Bioanalytical toxicology


Metrology needs and NIST resources for the forensic DNA community by Michael D. Coble; Margaret C. Kline; John M. Butler (pp. 293-297).
With the advent of forensic DNA profiling in the mid-1980s, this technology has had a positive impact on the criminal justice system, helping to convict the guilty and exonerate the innocent. The field has evolved from focusing on multilocus markers throughout the nuclear DNA genome to the use of autosomal short tandem repeat (STR) markers. Other marker systems such as mitochondrial DNA and Y-chromosomal STR testing have also found an important niche for the identification of missing persons and historical investigations. Given the importance of forensic DNA testing, it is critical that laboratories include proper controls and validated procedures for making quality measurements. In the United States, the National Institute of Standards and Technology (NIST) developed several standard reference materials (SRMs) to meet the needs of the forensic DNA community. Here, we discuss a brief history of forensic DNA testing and the development of NIST SRMs and educational resources for the field over the last 20 years.

Keywords: National Institute of Standards and Technology (USA); Standard reference materials; Short tandem repeat; DNA quantification; STRBase; Forensic DNA testing


Evaluation of three applications of a semi-automated most-probable-number method for the assessment of microbiological parameters in dairy products by U. Zitz; K. J. Domig; A. Hoehl; H. Weiss; P-Th. Wilrich; W. Kneifel (pp. 299-309).
Several rapid and automated microbiological methods have been introduced by food control laboratories because they allow microbiological quality (e.g. contamination with spoilage microorganisms and/or pathogens) of products to be checked or hygiene monitoring undertaken during production. This study evaluated three applications of the TEMPO® system; an automated method based on the most-probable-number technique, performed in parallel with the relevant ISO standard method for comparison. Escherichia coli certified reference material and soft cheese samples contaminated artificially with E. coli were used throughout the study. Performance characteristics including precision, bias and limit of detection of E. coli (EC), coliforms (TC) and viable aerobic mesophilic microflora (TVC) were determined with particular attention given to low-level contamination, which typically occur in manufacturing and retail as well as storage and consumption at home. TEMPO® EC was more precise than TEMPO® TC whilst TEMPO® TVC showed the most variation. Moreover, higher numbers of E. coli were obtained with TEMPO® EC than TEMPO® TC. Reliability of the system depended on the specificity of detection of the targeted group of microorganisms as well on the method. Although, methods like TEMPO® offer convenience, they often lack the necessary clarity in terms of operational details, measurement principles and data processing necessary for reliable routine use. Installation of an ‘expert modus’ to facilitate access to original data would significantly increase commercial confidence in the application and use of these systems.

Keywords: Coliforms; Dairy products; E. coli ; Most probable number; Precision; TEMPO


Mass balance method for purity assay of phthalic acid esters: development of primary reference materials as traceability sources in the Japan Calibration Service System by Keiichiro Ishikawa; Nobuyasu Hanari; Yoshitaka Shimizu; Toshihide Ihara; Akira Nomura; Masahiko Numata; Takashi Yarita; Kenji Kato; Koichi Chiba (pp. 311-322).
Purity assay of high-purity materials (HPMs) of phthalic acid esters (PAEs) was carried out by means of a mass balance method. In this method, chromatographic methods such as gas chromatography-flame ionization detector (GC-FID) and/or high-performance liquid chromatography (HPLC) in combination with other methods such as Karl-Fischer (KF) titration and vacuum evaporation (VE) were applied. The sum of the impurities estimated by these methods allowed the estimation of the purity of the main component by difference. Seven PAEs with varying side chain structures and levels of impurities were analysed on a systematic way in which impurities were classified into several groups in terms of their abundance, availability of qualitative information and availability of authentic compounds, etc. The absolute quantity of each impurity was determined by GC-FID and/or HPLC based on the calibration made by the authentic compounds of impurities whenever available. The purities in mass fraction of these PAEs were certified at the National Metrology Institute of Japan (NMIJ), and the PAEs were registered as primary reference materials playing an essential role in linking the metrological traceability of the Japan Calibration Service System (JCSS) to the International System of Units (SI).

Keywords: Certified reference material; Phthalic acid ester; Purity; Japan Calibration Service System; Mass balance method

Erratum to: Mass balance method for purity assay of phthalic acid esters: development of primary reference materials as traceability sources in the Japan Calibration Service System by Keiichiro Ishikawa; Nobuyasu Hanari; Yoshitaka Shimizu; Toshihide Ihara; Takeshi Saito; Akira Nomura; Masahiko Numata; Takashi Yarita; Kenji Kato; Koichi Chiba (pp. 323-323).

Parameters in cause and effect diagram for uncertainty evaluation by Jongseon Park; Gyeonghee Nam; JongOh Choi (pp. 325-326).
The cause and effect analysis is very useful tool to identify the sources, to ensure comprehensive coverage, and to avoid overcounting of uncertainty components. It is shown that the parameters in cause and effect diagram shall be the uncertainty components for major categories, subcategories, and effect rather than quantities. A pitfall is exemplified when the parameters in the diagram are mixed with quantities and uncertainty components.

Keywords: Uncertainty; Cause and effect analysis; Parameters; Input quantity

About measuring systems and measurement procedures by Xavier Fuentes-Arderiu (pp. 329-329).
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