Results from an amino acid racemization inter-laboratory proficiency study; design and performance evaluation |
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| Institution: | 1. BioArCh, Department of Archaeology, University of York, Wentworth Way, Heslington, York YO10 5DD, UK;2. BioArCh, Department of Chemistry, University of York, Heslington, York YO10 5DD, UK;3. YCCSA, Department of Computer Science, University of York, Heslington, York YO10 5GH, UK;4. Department of Palaeontology, Natural History Museum, Cromwell Road, London SW7 5BD, UK;1. School of Pharmacy, Università degli Studi di Camerino, via S. Agostino 1, 62032 Camerino, MC, Italy;2. Jurusan Kimia, FMIPA Universitas Negeri Malang, Jalan Surabaya 6, Malang 65145, Indonesia;3. Chemistry, School of Molecular Sciences, University of Western Australia, M310, 35 Stirling Highway, 6009 Perth, WA, Australia;4. School of Science and Tecnologies, Università degli Studi di Camerino, via S. Agostino 1, 62032 Camerino, MC, Italy;5. Istituto di Chimica dei Composti Organometallici (ICCOM-CNR), Via Madonna del Piano 10, 50019 Sesto Fiorentino Firenze, Italy;1. Clinical Chemistry Department, Isala, Dr. Van Heesweg 2, Zwolle 8025 AB, The Netherlands;2. European Reference Laboratory for Glycohemoglobin, Isala, Dr. Van Heesweg 2, Zwolle 8025 AB, The Netherlands;3. Faculty of Medicine and Health, School of Health Science, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK;1. State Key Laboratory Cultivation Base for the Chemistry and Molecular Engineering of Medicinal Resources, School of Chemistry & Pharmaceutical Science of Guangxi Normal University, Yucai Road 15, Guilin 541004, Guangxi, PR China;2. Department of Chemistry & Pharmaceutical Science, Guilin Normal College, Xinyi Road 15, Guangxi 541001, PR China;1. BioArCh, Departments of Archaeology and Chemistry, University of York, Heslington, York YO10 5DD, UK;2. Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands;3. NTNU University Museum, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway;4. Department of Conservation, University of Gothenburg, Box 130, SE-405 30 Gothenburg, Sweden;1. Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, PR China;2. Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port St. Lucie, FL 34987, USA |
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| Abstract: | It is nearly thirty years since the last inter-laboratory study was carried out for amino acid racemization (AAR) analysis using powdered fossil material (Wehmiller 1984). Since then there have been major changes in sample preparation and instrumentation, and it was considered timely to coordinate a new inter-laboratory study in support of current methodologies. In 2010, two such studies were undertaken. The first of these, coordinated by Wehmiller (this edition), used homogeneous hydrolysates of Pleistocene mollusc and eggshell materials and focused on the agreement of analytical measurements between laboratories, without interference from differing sample preparation procedures. The second (this study) was designed specifically as a proficiency test. Unlike previous inter-laboratory comparisons that have focussed on precision estimates, the purpose of this study was to carry out an evaluation of measurement bias by comparing the measurement results of laboratories carrying out their routine methods, including extraction, against the consensus values. Participants were sent one dried sample of a mixed amino acid standards solution and five homogeneous powders: two Pleistocene mollusc test materials prepared from material (ILC-A) supplied and used by Wehmiller in previous inter-laboratory studies (1984; and this edition), one Pleistocene opercula test material from the terrestrial gastropod, Bithynia tentaculata, and two heat-treated modern ostrich eggshell test materials. Results from this study demonstrate that whilst individual laboratory precision may be excellent, suggesting good control of random error influences (less than 1% for replicate measurements by some individual laboratories), agreement between methods, or even between laboratories carrying out the same method, may be very different. Trueness evaluation (determined as the relative percentage bias) reveals the extent of the disagreement reflected by the inter-laboratory variability. Individual laboratory D/L value biases of 10–30% or more when compared to the consensus values are not uncommon. We demonstrate why bias contributions should also be included in AAR uncertainty estimation and recommend that the preparation of defined reference materials are seen as a priority in order to control and correct for systematic error influences in the analytical system. |
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