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Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement (v.12, #3-4)
Improving data quality in food composition databanks: a EuroFIR contribution by Isabel Castanheira; Catarina André; Marine Oseredczuk; Jayne Ireland; Linda Owen; Paul Robb; Amanda Earnshaw; Maria Antónia Calhau (pp. 117-125).
Food composition databanks (FCDBs) should provide nutrient composition data comparable over time at national and international levels. However, the linkage between national database compilers and permanent structures to support the upgrading and monitoring of nutrient values in foods are far from satisfactory. This paper focuses on European efforts to improve the quality of nutrient values entered into FCDBs, emphasizing initiatives under the EU Network of Excellence: European Food Information Resource (EuroFIR – NoE). The general concept of quality assurance is described and results obtained in the project’s first year are presented. A survey among EuroFIR partners aimed at evaluating the current situation in comparability of nutrient values suggests that an integrated approach has two requirements: the implementation of a quality management system (QMS) and a harmonized data-quality assessment system (DQAS) to select values from different sources. The use of reference materials (RMs) is a key criterion in deciding on comparability and reliability of candidate nutrient values. Consequently, results of a survey on food matrix reference materials are presented. These suggest that developments in RMs for nutrient analysis in foods have a great impact on the quality of data to be included in FCDBs.
Keywords: Data quality; Food composition; EuroFIR; Reference materials
Summary of reference materials for the determination of the nutrient composition of foods by Katherine M. Phillips; Wayne R. Wolf; Kristine Y. Patterson; Katherine E. Sharpless; Karen R. Amanna; Joanne M. Holden (pp. 126-133).
Certified reference materials (CRMs) play a critical role in validating the accuracy of nutrient data for food samples. A number of available food CRMs of differing matrix composition have assigned concentrations for various nutrients, along with associated uncertainty intervals (UIs) for those values. These CRMs have been used extensively in the United States Department of Agriculture’s (USDA) ongoing National Food and Nutrient Analysis Program (NFNAP) to monitor the accuracy of assays of key foods and nutrients consumed in the United States. A total of 690 assigned values for individual nutrients, including proximates, vitamins, macroelements, microelements, fatty acids, amino acids, and selected phytochemicals (e.g., carotenoids), were compiled from the certificates of analysis for 63 CRMs, and the specified UI in each case was expressed as a percentage of the assigned certified or reference concentration. Across all nutrients, 63.5% of the UIs were less than 10% of the assigned value, 25.5% were 10–20%, and 11% were greater than 20% of the assigned value. The UIs for proximates, minerals, and trace elements were most consistently less than 10% of the assigned value. The relative uncertainties were significantly higher for vitamins, suggesting greater challenges in measuring and certifying these components. These high UIs (greater than 10% assigned value) in the best available reference materials are likely to be indicative of the precision and accuracy that can be obtained by current measurement systems for these components. These data suggest that care must be taken in choosing CRMs to monitor food composition analysis, including evaluating what levels of uncertainty are required in assigned values and which analytical measurement systems for food components need closer examination and improvement.
Keywords: Reference materials; Food composition data
Development of reference materials for microbiological analysis by Wolfgang J. Philipp; Pierre van Iwaarden; Heinz Schimmel; Nele Meeus; Nadine Kollmorgen (pp. 134-138).
The reliability of reference materials (RMs) depends on properties such as fitness, robustness, commutability, stability and homogeneity. The development of RMs for microbiological analysis is especially challenged through questions around the stabilisation and recovery of viable cells, the dispersion of precise numbers of cells, matrix effects and, when using molecular techniques, the presence of nucleic acids (e.g. DNA) of dead and live target organisms. However, RMs are indispensable tools for quality control in microbiological analysis. The Institute for Reference Materials and Measurements (IRMM), as part of the European Commission, concentrates its efforts on the development of RMs to support the development, implementation and monitoring of EU legislation. A special focus is given to highly precise RMs for presence/absence and enumeration tests in microbiological food and water analysis. Another group of new RMs certified by the IRMM comprise DNA-based materials to control the identity of micro-organisms in qualitative assays. All of these activities serve to improve quality control in microbiological analysis.
Keywords: Reference materials; Microbiological analysis; Quality control; Food microbiology; Water microbiology; Pathogens
Analytical validation of quality control materials for Huntington’s disease examination by John P. Jakupciak; Kristy L. Richie (pp. 139-145).
The expansion of molecular diagnostics using nucleic acid technologies in clinical and public health practice has increased the need for appropriate reference materials and verified quality-control materials for quality assurance, test validation, proficiency testing and the development of new examination procedures. Good laboratory practice requires the use of reference materials to establish an examination procedure and assess the variability of the results. Reference materials are also required to assess the assay on a daily basis and to normalize results collected among different laboratories. Despite the growing volume, the rapidly increasing number of tests being offered, and the necessary routine use, certified reference materials are often not available. There is a wide range of human genetic bio-assays for which there are no available traceable certified reference materials. Several initiatives have been organized to provide well-characterized quality control specimens (e.g., cell lines) with known DNA mutations for use in diagnostics. Mutations are confirmed with bi-directional DNA sequence analysis, which is considered the reference examination procedure. In the field of personalized medicine, NIST has created and validated Standard Reference Material® 2399 for fragile X examinations. Herein we describe our characterization of candidate reference materials for Huntington’s disease genetic examination. Bi-directional DNA sequencing confirmed the size of the CAG repeat contained on each allele from patient derived materials. Amplification and capillary electrophoresis of the CAG repeats had an uncertainty ranging from 2.06%CV to 7.83%CV.
Keywords: DNA sequencing; Electrophoretic sizing; Genetic examination; CAG triplet repeats; Huntington’s disease
Creatinine determination in urine from the point of view of reference values by Josef Kratochvíla; Bedřich Friedecký; Marek Budina; Ilona Šperlingová (pp. 146-150).
In this paper, the creation of a certified reference material for urinary creatinine is described. We used the Jaffe method and HPLC method for establishment of the certified value. Homogeneity tests are also described. We obtained material with sufficient homogeneity, stability, and with certified value (expanded uncertainty, k=2 for CI 95%) (7.77±0.27) mmol·L−1. This material was consequently used for the interlaboratory comparison (EQA Czech Republic for clinical chemistry). Twenty-nine percent of the participants obtained measurement results within the interval of the certified value ± expanded uncertainty, while 85% of the participants obtained values inside the interval of the certified value ± target measurement uncertainty. Direct use of the certified reference materials for method evaluation in EQA programs means a significant advance for monitoring and documentation traceability of results in routine measurements.
Keywords: Creatinine; Urine; Homogeneity; Certification; Uncertainty; EQA
Determination of the purity of acidimetric standards by constant-current coulometry, and the intercomparison between CRMs by Toshiaki Asakai; Mariko Murayama; Tatsuhiko Tanaka (pp. 151-155).
The accuracy and uncertainty of the coulometric measurement results of reference materials for acidimetric titration were examined in this study. The results for amidosulfuric acid and potassium hydrogen phthalate are presented. The uncertainty was investigated by examining the dependency on the sample size and on the electrolysis current. Changes in the titration parameters did not result in any significant effects on the titration results. Acidimetric standards with the certified value linked to the SI were developed. In addition, the intercomparison of acidimetric standards was carried out by gravimetric titration, and the relationship between our coulometric results was determined. Furthermore, due to recent internationalization, not only the traceability to the SI but also the relationship and consistency of their analytical data have gained increasing importance. Our results were validated using certified reference materials (CRMs) obtained from different National Metrology Institutes (NMIs), and their relationships are presented.
Keywords: Coulometry (constant-current); Stoichiometric standards; Potassium hydrogen phthalate; Amidosulfuric acid
Matrix certified reference materials for environmental monitoring from the National Metrology Institute of Japan (NMIJ) by Takashi Yarita; Akiko Takatsu; Kazumi Inagaki; Masahiko Numata; Koichi Chiba; Kensaku Okamoto (pp. 156-160).
Matrix certified reference materials (CRMs) are playing an increasingly important role in environmental monitoring in Japan. The National Metrology Institute of Japan (NMIJ)/National Institute of Advanced Industrial Science and Technology (AIST) has been developing matrix CRMs for environmental monitoring since 2001, and has issued nine kinds of CRMs as NMIJ CRMs. The development of the CRMs was conducted in NMIJ in cooperation with candidate material producers. The isotope dilution mass spectrometry (IDMS) was principally adopted to give reliable certified values. Meanwhile, two or more analytical methods, whose levels of accuracy were well evaluated, were applied to avoid any possible analytical bias. Two typical certification processes, the certification of river water CRMs for trace element analysis and that of marine sediment CRMs for PCB and organochlorine pesticide analysis, are outlined as examples.
Keywords: Certified reference material; Certification; Matrix reference material; Traceability; Environmental monitoring
Reference material in residue control: assessment of matrix effects by Petra Gowik; Joachim Polzer; Steffen Uhlig (pp. 161-166).
The production of certified reference materials (CRM) requires a comprehensive consideration of which analytes and materials to select. The present study describes the pre-tests for the production of CRM for nitroimidazoles in plasma or muscle. By means of a commutability study, four factors, namely matrix (plasma – muscle), species (turkey – pig), matrix condition (fresh - lyophilized) and measurement technique (GC-NCI/MS-LC-MSMS) were checked for their usability. The results showed that the matrices, matrix conditions, as well as the species analyzed did not produce any relevantly different measurement results. Varying significantly and subject to a systematic error were those results which were determined by means of different measurement techniques.
Keywords: Commutability study; CRM; OptiVal; InterVal; Experimental design
Accreditation of reference material producers: the example of IRMM's Reference Materials Unit by Thomas P J Linsinger; Alexander Bernreuther; Philippe Corbisier; Marta Dabrio; Håkan Emteborg; Andrea Held; Andrée Lamberty; Gaida Lapitajs; Marina Ricci; Gert Roebben; Stefanie Trapmann; Franz Ulberth; Hendrik Emons (pp. 167-174).
The potential approaches for third-party assessment of reference material producers are revisited and the activities of the Reference Materials (RM) Unit of the Institute for Reference Materials and Measurements (IRMM) to obtain accreditation to ISO Guide 34 and ISO 17025 are described. Accreditation was related to the Unit as all matrix RM activities of the institute are concentrated there. A management system was established that allows sufficient flexibility to be applicable to a wide range of RMs while being precise enough to ensure compliance with ISO Guides 30, 31 and especially 34 and 35. Accreditation was achieved in 2004 with independent scopes for testing and RM production and was confirmed and extended in 2005. The key aspects of the RM Unit's management system for RM production are presented.
Keywords: Accreditation; Reference materials; Third-party assessment; RM; CRM; ISO Guide 34
Description and results of the NIST/NOAA 2005 Interlaboratory Comparison Exercise for Trace Elements in Marine Mammals by Steven J. Christopher; Rebecca S. Pugh; Michael B. Ellisor; Elizabeth A. Mackey; Rabia O. Spatz; Barbara J. Porter; Kathie J. Bealer; John R. Kucklick; Teri K. Rowles; Paul R. Becker (pp. 175-187).
The National Institute of Standards and Technology’s (NIST) National Marine Analytical Quality Assurance Program (NMAQAP) is dedicated to improving the quality of analytical measurements of trace elements, organic contaminants and emerging compounds of concern in marine and environmental systems, through various quality assurance mechanisms, including analytical method development and value assignment, quality assurance materials production, cryogenic marine specimen archival and the coordination of interlaboratory comparison exercises. This report focusses on the description and results of the 2005 Interlaboratory Comparison Exercise for Trace Elements in Marine Mammals. This program is co-sponsored by the National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Office of Protected Resources, specifically, the Marine Mammal Health and Stranding Response Program. Two quality control materials derived from fresh-frozen marine mammal livers were produced and characterised at the NIST and were then distributed to over 30 laboratories. A maximum likelihood solution model was used to assign consensus data that served as a benchmark for comparison, and a series of group metrics were generated to assist the laboratories with the interpretation of performance and analytical assessment.
Keywords: Consensus mean; Interlaboratory comparison exercise; Maximum likelihood; Marine mammals; Trace elements
The preparation, assay and certification of aqueous ethanol reference solutions by Marcellé Archer; Betty-Jayne de Vos; Maria S Visser (pp. 188-193).
Internationally, certified ethanol reference materials are required to calibrate breathalysers and blood-alcohol measurement instruments. The CSIR National Metrology Laboratory of South Africa provides certified aqueous ethanol solutions with traceability to the SI. Ethanol solutions in the concentration range 10 mg/100 g to 20 g/100 g are prepared gravimetrically by mixing ethanol and reagent quality water. To verify the concentration of the ethanol it is oxidized to acetic acid with potassium dichromate in the presence of sulphuric acid. The unreacted potassium dichromate is back-titrated with sodium thiosulphate. The method utilizes gravimetry and titrimetry, which are both primary methods. This paper addresses aspects of ethanol-certified reference materials that have not been previously published: traceability, stability of unpreserved ethanol solutions, homogeneity, quality control measures and the effect of reproducibility on the measurement uncertainty.
Keywords: Ethanol; Certified reference material; Traceability; Titrimetry; Gravimetry; Primary methods
Development of metrology for pH measurement in Thailand by Bunthoon Laongsri; Cheerapa Boonyakong; Nongluck Tangpaisarnkul; Chainarong Cherdchu (pp. 194-200).
It has not been long that metrology is well accepted as an important part in analytical chemistry since it helps the chemists to receive the best measurement and accurate results with traceability. The National Institute of Metrology Thailand (NIMT), which is a public agency under the supervision of the Ministry of Science and Technology, not only focuses on physical standards but also provides and maintains standards in chemical field. pH measurement is one of the most widely used in the laboratories including industries and medical area in Thailand. The chemical laboratory starts working on the project with the objective of disseminating an accurate result in routine pH measurement. In 2002, the laboratory provided a service in calibration of pH meter and organized the first local interlaboratory comparison program (NIMT–C-ILC-1: pH buffer) in pH measurement. There were three buffer solution samples in the range of acid, neutral, and base. A total of 44 laboratories participated in this program. The NIMT chemical laboratory also participated in the proficiency testing program that was conducted by PSB Corporation Testing Group in Singapore. In 2003, NIMT started research in preparation of secondary buffers by using highly accurate pH meters with glass electrode systems. The laboratory produced three secondary buffers, which were pH 4.01, 6.86, and 9.18 with uncertainty 0.020 pH at 25°C. The competence of the laboratory was shown by the measurement results of the pilot study (APMP.QM-P06), which was organized by the APMP electrochemical analysis working group (EAWG/TCQM) in 2005. The title of this study was “pH determination of two phosphate buffers by Harned cell method and glass electrode method”. NIMT aims to achieve for establishment of the primary method for pH measurement in the near future.
Keywords: pH measurement; Interlaboratory; Buffer; pH
Evolution of philosophy and description of measurement (preliminary rationale for VIM3) by Charles Ehrlich; René Dybkaer; Wolfgang Wöger (pp. 201-218).
Different approaches to the philosophy and description of measurement have evolved over time, and they are still evolving. There is not always a clear demarcation between approaches, but rather a blending of concepts and terminologies from one approach to another. This sometimes causes confusion when trying to ascertain the objective of measurement in the different approaches, since the same term may be used to describe different concepts in the different approaches. Important examples include the terms “value,” “true value,” “error,” “probability” and “uncertainty.” Constructing a single vocabulary of metrology that is able to unambiguously encompass and harmonize all of the approaches is therefore difficult, if not impossible. This paper examines the evolution of common philosophies and ways of describing measurement. Some of the differences between these approaches are highlighted, which provides a rationale for the entries and structure of the August 2006 draft of the 3rd Edition of the International Vocabulary of Metrology – Basic and General Concepts and Associated Terms (VIM3) [1].