1、Reference materials Establishing and expressing metrological traceability of quantity values assigned to reference materials PD ISO/TR 16476:2016 BSI Standards Publication WB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06National foreword This Published Document is the UK implementation of IS
2、O/TR 16476:2016. The UK participation in its preparation was entrusted to Technical Committee RMI/1, Reference Materials. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a
3、contract. Users are responsible for its correct application. The British Standards Institution 2016. Published by BSI Standards Limited 2016 ISBN 978 0 580 79297 7 ICS 71.040.30 Compliance with a British Standard cannot confer immunity from legal obligations. This Published Document was published un
4、der the authority of the Standards Policy and Strategy Committee on 30 June 2016. Amendments/corrigenda issued since publication Date Text affected PUBLISHED DOCUMENT PD ISO/TR 16476:2016 ISO 2016 Reference materials Establishing and expressing metrological traceability of quantity values assigned t
5、o reference materials Matriaux de rfrence Etablissement et expression de la traabilit mtrologique de valeurs assignes des matriaux de rfrence TECHNICAL REPORT ISO/TR 16476 Reference number ISO/TR 16476:2016(E) First edition 2016-06-01 PD ISO/TR 16476:2016 ISO/TR 16476:2016(E)ii ISO 2016 All rights r
6、eserved COPYRIGHT PROTECTED DOCUMENT ISO 2016, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an
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8、iso.org www.iso.org PD ISO/TR 16476:2016 ISO/TR 16476:2016(E)Foreword iv Introduction v 1 Scope . 1 2 The VIM definition of metr ological tr ac eability 1 3 Challenges arising fr om the definition of metr ological tr ac eability 2 3.1 Conventions . 2 3.2 (C)RM as the carrier of traceable values. 3 3
9、.3 Implicit traceability to the unit of the measurement scale . 4 3.4 Traceability networks . 5 3.5 Properties expressed in units of measurement scales other than the SI 5 3.6 Properties other than quantitative 6 3.7 Summary of an ISO/REMCO event on metrological traceability . 6 4 Approaches to metr
10、ological traceability of (C)RM 7 4.1 General . 7 4.2 Approach A . 7 4.3 Approach B . 8 5 Establishing traceability of (C)RM property values (Approach B) . 9 5.1 Principles . 9 5.2 Traceability pathways 10 5.3 Steps in establishing traceability .10 5.3.1 General.10 5.3.2 Combining results 11 5.4 Summ
11、ary .12 6 Reporting traceability 12 6.1 Inquiry .12 6.2 Results of the inquiry .12 6.3 Requirements 13 6.4 Formats .14 6.5 Further recommendations .16 Annex A (informative) Worked-out example 17 Annex B (informative) Catalogue of analytes and measurement areas covered by WHO 19 Annex C (informative)
12、 Example for method-independent, SI traceable values obtained by inter-laboratory comparison 21 Bibliography .22 ISO 2016 All rights reserved iii Contents Page PD ISO/TR 16476:2016 ISO/TR 16476:2016(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of nat
13、ional standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. Interna
14、tional organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. The procedures used to develop this document and those inten
15、ded for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.
16、iso.org/directives). Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document w
17、ill be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents). Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement. For an explanation on the meaning of ISO specific terms and expr
18、essions related to conformit y assessment, as well as information about ISOs adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html. ISO/TR 16476 was prepared by the ISO Committee on Reference Materials
19、 (ISO/REMCO).iv ISO 2016 All rights reserved PD ISO/TR 16476:2016 ISO/TR 16476:2016(E) Introduction Reference materials (RM), in particular when certified (CRM), are a major tool for assuring the quality and reliability of results obtained in measurement and testing. CRM property values, in particul
20、ar used for assessing the trueness of a measurement procedure as implemented in a laboratory, also establish traceability of the measurement result. Which reference the property values assigned to (C)RM should be traceable to, and how this traceability should be established, demonstrated, and report
21、ed on certificates is, therefore, a question of primary importance, mainly for RM producers. However, users of (C)RMs should also know what the endpoint of their traceability chain is, in particular for all purposes of cross-border acceptance of measurement results. It was therefore considered neces
22、sary to conduct a study into existing principles for, and requirements to, the traceability of (C)RM, in particular with a specific view to the current definition of metrological traceability given by the Vocabulary of International Metrology (VIM), edition 3, 2007. ISO 2016 All rights reserved v PD
23、 ISO/TR 16476:2016 Reference materials Establishing and expressing metrological traceability of quantity values assigned to reference materials 1 Scope This Technical Report investigates, discusses, and specifies further, the general principles of establishing traceability of measurement results lai
24、d down in the Joint BIPM, OIML, ILAC and ISO Declaration on Metrological Traceability1 , in particular for values assigned to (certified) reference materials. The document covers the following topics: a) a study into existing principles for, and requirements to, the traceability of the value assigne
25、d to the property of a (C)RM, with a specific view to the current definition of metrological traceability given by the 2007 edition of the VIM (published also as JCGM 200:2008 2and ISO/IEC Guide 99:2007 21 ); b) the development of a sensible, widely applicable approach to the understanding of the tr
26、aceability of a value assigned to (C)RM property; c) recommendations on how traceability should be established, demonstrated, and reported on certificates and other documents accompanying (C)RM. The developed approach is exemplified for measurement procedures not covered earlier by other guidance do
27、cuments on the topic. 2 The VIM definition of metr ological tr ac eability The recent edition of the VIM 2,21defines metrological traceability (term 2.41) as property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each co
28、ntributing to the measurement uncertainty NOTE 1 For this definition, a reference can be a definition of a measurement unit through its practical realization, or a measurement procedure including the measurement unit for a non-ordinal quantity, or a measurement standard. NOTE 2 Metrological traceabi
29、lity requires an established calibration hierarchy. NOTE 3 Specification of the reference must include the time at which this reference was used in establishing the calibration hierarchy, along with any other relevant metrological infor- mation about the reference, such as when the first calibration
30、 in the calibration hierarchy was performed. NOTE 4 For measurements with more than one input quantity in the measurement model, each of the input quantity values should itself be metrologically traceable and the calibration hierarchy involved may form a branched structure or a network. The effort i
31、nvolved in establishing metrological traceability for each input quantity value should be commensu- rate with its relative contribution to the measurement result. NOTE 5 Metrological traceability of a measurement result does not ensure that the measurement uncertainty is adequate for a given purpose
32、 or that there is an absence of mistakes. TECHNICAL REPORT ISO/TR 16476:2016(E) ISO 2016 All rights reserved 1 PD ISO/TR 16476:2016 ISO/TR 16476:2016(E) NOTE 6 A comparison between two measurement standards may be viewed as a calibration if the comparison is used to check and, if necessary, correct
33、the quantity value and measure- ment uncertainty attributed to one of the measurement standards. NOTE 7 The ILAC considers the elements for confirming metrological traceability to be an un- broken metrological traceability chain to an international measurement standard or a national measurement stan
34、dard, a documented measurement uncertainty, a documented measurement procedure, accredited technical competence, metrological traceability to the SI, and calibration intervals (see ILAC P-10:2002). NOTE 8 The abbreviated term “traceability” is sometimes used to mean metrological traceabil- ity as we
35、ll as other concepts, such as sample traceability or document traceability or instrument traceability or material traceability, where the history (“trace”) of an item is meant. Therefore, the full term of “metrological traceability” is preferred if there is any risk of confusion. NOTE 7 makes clear
36、that the measurement method/procedure is a part of the traceability statement, but insufficient if taken alone. This implies that a measurement result or the assigned value of a (C)RM can be traceable to a method or a series of methods used, but not to the method alone, although such statements can
37、still be found on CRM certificates. Without any doubt, the measurement procedure used will mostly be reflected in the definition of the measurand, but additionally, the value assigned to the measurand has to be made traceable to stated references given the procedure applied, thus, the latter cannot
38、be the endpoint of the traceability chain for the assigned value. Recent presentations on the topic (e.g. Reference3) support this viewpoint. As expressed in NOTE 2, the definition as given above is governed by the (assumed) existence of a straightforward, single-route top-down reference standard hi
39、erarchy. Reference 4, as a guidance to implement the above VIM definition in chemistry, almost always assumes the existence of higher-order reference materials, conveniently certified at the highest level by using allegedly primary methods. This Technical Report does not go into further details of t
40、hese situations since References 4 to 6 provide sufficient guidance. Considerations and guidance on traceability hierarchies together with graphs visualizing and illustrating traceability chains, including branched ones, can also be found in Reference 7. The described philosophy works fine for all l
41、evels which still have a “higher-order” level above, or fields where primary methods exist and can readily be used for a valid and reliable value assignment to the measurand. However, at some point, the top with no “higher-order” is reached. It may also be stated that for a huge amount of certified
42、reference materials at this level, no primary method is available for assigning values to the measurands. This causes the general problem of traceability for property values of (C)RMs allocated at prominent places in the hierarchy. More critical points will be discussed under Clause 3. NOTE An annot
43、ation document is being developed. Its aim is to give further explanations to the VIM definitions; it will also provide advice regarding the application of these definitions. 3 Challenges arising fr om the definition of metr ological tr ac eability 3.1 Conventions For the purposes of this Technical
44、Report, the following conventions apply. “Traceability of an RM” is in common and daily use, it is understood throughout as the traceability of the quantity value assigned to a (certified) reference material. “(Analytical) method” is used in the sense of defining the instrumental implementation of t
45、he (most often physical) principle of obtaining, from an appropriately pre-processed and/or transformed object under 2 ISO 2016 All rights reserved PD ISO/TR 16476:2016 ISO/TR 16476:2016(E) investigation, a signal (subject to further processing) reflecting the sought-after property. Such implementat
46、ions are, for example, ToF-IDMS, GC-FID, LC-MS/MS, HPLC-DAD, FT-IR, etc. “Measurement protocol” is used to refer to measurement procedures prescribed or standardized to an extent that the value(s) assigned to the material becomes senseless without direct reference to these prescriptions, i.e. where
47、not only the conditions under which measurements have to be taken but also form, structure, shape, size and/or composition of the specimen are prescribed. “RM document”, sometimes also called “property value sheet” or “product information sheet” (see ISO Guide 31) is used as an analogue to, and dist
48、inction from, the term “certificate” as defined in ISO Guide 31. Certificates refer to CRM, while an RM document provides the necessary information on the properties of a (non-certified) RM. “Matrix (C)RM” an RM made out of natural-born substance(s) or synthetically re-constituted ingredients, chara
49、cterised for composition. “Property (C)RM” an RM characterized for a property other than the content of main components and/or impurities as e.g. tensile strength or Charpy impact for an alloyed steel. NOTE This Technical Report refers to the requirements of ISO Guide 34, in force at the time of publication of this Technical Report. For traceability issues, the future ISO 17034 will also follow the principles of the named ISO Guide 34. 3.2 (C)RM as the carrier of traceable values In the contex
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