ISO-GUIDE-32-1997.pdf
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1、STD-IS0 GUIDE 32-ENGL 1997 4851903 0735093 979 GUIDE 32 Calibration in analytical chemistry and use of certified reference ma ter i a Is This material is reproduced from IS0 documents under International Organization for Standardization (ISO) Copyright License number IHSIICC11996. Not for resale. No
2、 part of these IS0 documents may be reproduced in any form, electronic retrieval system or otherwise, except as allowed in the copyright law of the country of use, or with the prior written consent of IS0 (Case postale 56,121 i Geneva 20, Switzerland, Fax +41 22 734 10 79), IHS or the IS0 Licensors
3、members. First edition 1997 -,-,- STD-IS0 GUIDE 32-ENGL 1997 9851703 0735094 805 IS0 GUIDE 32:1997(E) Foreword IS0 (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies t
4、hat are members of IS0 or IEC participate in the development of International Standards through technical committees established by the respective organization to deal with particular fields of technical activity. IS0 and IEC technical committees collaborate in fields of mutual interest. Other inter
5、national organizations, governmental and non-governmental, in liaison with IS0 and IEC, also take part in the work. Draft Guides adopted by the responsible Committee or Group are circu- lated to national bodies for voting. Publication as a Guide requires approval by at least 75 % of the national bod
6、ies casting a vote. IS0 Guide 32 was prepared by the IS0 Committee on Reference Materials (REMCO). O IS0 1997 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and m
7、icrofilm, without permission in writing from the publisher. International Organization for Standardization Case postale 56 CH-1 21 1 Genve 20 Switzerland internet central Q iso.ch X.400 c=ch; a400net; p=iso; o=isocs; s=central Printed in Switzerland ii -,-,- STDmISO GUIDE 32-ENGL 1997 H 4853703 0735
8、075 743 W 0 IS0 IS0 GUIDE 32:1997(E) Introduction Within the framework of the International Laboratory Accreditation Conference (ILAC), held in Torino (Italy) in October 1990, a one-day technical seminar was devoted to Metrology in testing where the various aspects of metrological traceability in di
9、fferent fields of testing were addressed. In order to clarify the implementation of the principles of metrological traceability in chemistry, it was then requested that an ILAC Guide be established on Calibration in analytical chemistry and use o f certified reference materiais. A draft was establis
10、hed which, after amendments by an ILAC Working Group, was approved by the 1992 ILAC Conference in Ottawa (Canada). Moreover, due to a worldwide need for such information, it was further recommended to transmit this draft to ISO/REMCO to serve as basis for development of an IS0 Guide. This proposal w
11、as accepted by ISO/REMCO. Finalization of this Guide was carried out by ISO/REMCO Task Group 2, Calibration. iii -,-,- Calibration in analytical chemstry and use of certified reference materials 1 Scope Quality assurance in a testing laboratory, particularly in the case of its assessment (see ISO/IE
12、C Guide 25), highlights the need to consider closely the question of the accuracy of its measurements and analytical results, and to ensure that the principles necessary to establish demonstrated accuracy have not been omitted. The calibration of the parameters associated with chemical analyses and
13、material testing deserves particular attention, because major errors can be made by neglecting or ignoring the basic principles of metrology which also apply to these areas. This Guide identifies a number of general recommendations for those who, either in laboratories or as assessors, are faced wit
14、h this problem. 2 References ISO/IEC Guide 25:1990, General requirements for the competence of calibration and testing laboratores. IS0 Guide 30:1992, Terms and definitions used in connection with reference materials. IS0 Guide 31 :1981, Contents of certificates of reference materials. IS0 Guide 33:
15、1989, Uses of certified reference materials. IS0 Guide 34:1996, Qualify system guidelines for the production of reference materials. IS0 Guide 35:-, Certification of reference materials - General and statistical principles. VIM:1993, International vocabulary of basic and general terms in metrology.
16、BIPM, IEC, IFCC, ISO, IUPAC, IUPAP, OIML. Guide to the expression of uncertainty in measurement. 1 st edition, 1993 (corrected and reprinted 1995). 3 Basic considerations Any measurement, particularly any quantitative chemical analysis, shall employ reference elements to ensure demonstrated traceabi
17、lity to the relevant basic quantities. This is an essential condition for the accuracy of the results. The metrological quality of the calibration performed depends on: To be published. (Revision of IS0 Guide 35:1989) -,-,- STD-IS0 GUIDE 32-ENGL L977 ir851703 0735077 514 IS0 GUIDE 32:1997(E) IS0 o t
18、he uncertainty of the reference used (set of calibration masses, titrated solutions, gas mixtures, composition CRMS, etc.), the appropriateness (or fitness for purpose) of this reference under the practical conditions of use, also taking into account the analytical method used and the tested samples
19、. The uncertainty of calibration results from these two components, and it has to be optimized without ignoring either of them. The analyst should compare the uncertainty of calibration with the required uncertainty of the analysis (which, normally, should be agreed between the customer and the oper
20、ator). This comparison provides a useful guide for choosing between different available calibration procedures and, in the longer term, for improvements to the methods and procedures. In tests based on measurements of physical quantities, the principle of traceability of the standards and/or measuri
21、ng instruments of the accredited laboratory to a national primary standard through a national calibration system, is generally applied. Relevant principles for ensuring the traceability of chemical analyses are presented later in this document: the use of CRMs for that purpose has been gaining impor
22、tance in the last decades and may be expected to develop even more, if and when they are available. 4 Selection of calibration procedures i n chemical analysis 4.1 Types of analytical procedures The first step consists in classifying the analytical procedure used into one of the following categories
23、 : 0 Type I 0 Type II 0 Type III each of these categories being associated with : a basic principle a number of basic prerequisites. When the user classifies a method, it should be done by means of a detailed and close examination of all the parameters of the analytical procedure. He/she must never
24、be satisfied with simplifications which would only be applicable to the detection principle applied under idealized conditions. This approach generally results in underestimating the necessary conditions for a reliable calibration and of generating systematic errors. Calibration does not make an ina
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