1、BS ISO 8196-2:2009 ICS 67.100.10 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BRITISH STANDARD Milk Definition and evaluation of the overall accuracy of alternative methods of milk analysis Part 2: Calibration and quality control in the dairy laboratoryThis British Standard
2、 was published under the authority of the Standards Policy and Strategy Committee on 30 November 2009. BSI 2009 ISBN 978 0 580 58448 0 Amendments/corrigenda issued since publication Date Comments BS ISO 8196-2:2009 National foreword This British Standard is the UK implementation of ISO 8196-2:2009.
3、The UK participation in its preparation was entrusted to Technical Committee AW/5, Chemical analysis of milk and milk products. 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
4、 of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal obligations.BS ISO 8196-2:2009Reference numbers ISO 8196-2:2009(E) IDF 128-2:2009(E) ISO and IDF 2009INTERNATIONAL STANDARD ISO 8196-2 IDF 128-2 Second edition 2009
5、-10-01 Milk Definition and evaluation of the overall accuracy of alternative methods of milk analysis Part 2: Calibration and quality control in the dairy laboratory Lait Dfinition et valuation de la prcision globale des mthodes alternatives danalyse du lait Partie 2: Calibrage et contrle qualit dan
6、s les laboratoires laitiers BS ISO 8196-2:2009 ISO 8196-2:2009(E) IDF 128-2:2009(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed
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11、 Brussels Tel. + 41 22 749 01 11 Tel. + 32 2 733 98 88 Fax + 41 22 749 09 47 Fax + 32 2 733 04 13 E-mail copyrightiso.org E-mail infofil-idf.org Web www.iso.org Web www.fil-idf.org Published in Switzerland ii ISO and IDF 2009 All rights reservedBS ISO 8196-2:2009 ISO 8196-2:2009(E) IDF 128-2:2009(E)
12、 ISO and IDF 2009 All rights reserved iiiContents Page Foreword iv Foreword .v Introductionvi 1 Scope1 2 Normative references1 3 Terms, definitions, and symbols .1 3.1 Terms and definitions .1 3.2 Symbols2 4 Calibration of instruments3 4.1 General principles .3 4.2 General procedure.3 4.3 Frequency
13、of calibration control .10 4.4 Centralized calibration11 5 Quality control in a routine dairy laboratory 11 5.1 Verification of repeatability 11 5.2 Daily check on short-term stability of the instrument .11 5.3 Verification of bias between laboratories .14 5.4 Verification of the difference between
14、reference and alternative method results14 5.5 Verification of the compliance of alternative method results with a compositional requirement16 6 Examples18 6.1 Calculation of statistical values.18 6.2 Determination of repeatability20 6.3 Verification of the exactness of the calibration .20 6.4 Deter
15、mination of accuracy .22 6.5 Checking the difference between reference and alternative method results .22 6.6 Conclusions .22 6.7 Verification of compliance with target values and upper or lower limits 23 Bibliography25 BS ISO 8196-2:2009 ISO 8196-2:2009(E) IDF 128-2:2009(E) iv ISO and IDF 2009 All
16、rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national 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 subjec
17、t for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC)
18、 on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committee
19、s are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. 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 he
20、ld responsible for identifying any or all such patent rights. ISO 8196-2|IDF 128-2 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF). It is being published jointly by ISO and IDF. This second edition
21、of ISO 8196-2|IDF 128-2 cancels and replaces the first edition (ISO 8196-2:2000), which has been technically revised. ISO 8196|IDF 128 consists of the following parts, under the general title Milk Definition and evaluation of the overall accuracy of alternative methods of milk analysis: Part 1: Anal
22、ytical attributes of alternative methods Part 2: Calibration and quality control in the dairy laboratory Part 3: Protocol for the evaluation and validation of alternative quantitative methods of milk analysis BS ISO 8196-2:2009 ISO 8196-2:2009(E) IDF 128-2:2009(E) ISO and IDF 2009 All rights reserve
23、d vForeword IDF (the International Dairy Federation) is a non-profit organization representing the dairy sector worldwide. IDF membership comprises National Committees in every member country as well as regional dairy associations having signed a formal agreement on cooperation with IDF. All members
24、 of IDF have the right to be represented at the IDF Standing Committees carrying out the technical work. IDF collaborates with ISO in the development of standard methods of analysis and sampling for milk and milk products. The main task of Standing Committees is to prepare International Standards. D
25、raft International Standards adopted by the Action Teams and Standing Committees are circulated to the National Committees for voting. Publication as an International Standard requires approval by at least 50 % of IDF National Committees casting a vote. Attention is drawn to the possibility that som
26、e of the elements of this document may be the subject of patent rights. IDF shall not be held responsible for identifying any or all such patent rights. ISO 8196-2|IDF 128-2 was prepared by the International Dairy Federation (IDF) and Technical Committee ISO/TC 34, Food products, Subcommittee SC 5,
27、Milk and milk products. It is being published jointly by ISO and IDF. All work was carried out by the Joint IDF-ISO Action Team on Automated methods of the Standing Committee on Quality assurance, statistics of analytical data and sampling under the aegis of its project leader, Mr. O. Leray (FR). Th
28、is edition of ISO 8196-2|IDF 128-2, together with ISO 8196-1|IDF 128-1 and ISO 8196-3|IDF 128-3, cancels and replaces IDF 128:1985, which has been technically revised. ISO 8196|IDF 128 consists of the following parts, under the general title Milk Definition and evaluation of the overall accuracy of
29、alternative methods of milk analysis: Part 1: Analytical attributes of alternative methods Part 2: Calibration and quality control in the dairy laboratory Part 3: Protocol for the evaluation and validation of alternative quantitative methods of milk analysis BS ISO 8196-2:2009 ISO 8196-2:2009(E) IDF
30、 128-2:2009(E) vi ISO and IDF 2009 All rights reservedIntroduction The main purpose of this part of ISO 8196|IDF 128 is to provide practical details and recommendations for the calibration of instruments and quality control in routine dairy laboratories, including the checking of compliance with a s
31、pecification value or limit. ISO 8196-1|IDF 128-1 is mainly intended for users to assess alternative methods of analysis and gives guidance for routine laboratories using these methods. This part of ISO 8196|IDF 128 relates directly to ISO 8196-1|IDF 128-1 for the definition of the relevant performa
32、nce characteristics, for the quantitative evaluation of the overall accuracy and the establishment of relevant standard limit values to comply with in analytical quality assurance as described. The general concepts apply to all analytical methods, but special emphasis is given to rapid physicochemic
33、al methods which are currently in use for the compositional testing of milk. ISO 8196|IDF 128 (all parts) only specifies the single linear regression model as a simplified approach to allow users to determine equivalence of an alternative method with a reference method. However, the linear regressio
34、n approach is valid as a determination of method equivalence only in limited circumstances or if a high correlation between the results of the reference method and the routine method is achieved. If a high correlation is not achieved, recourse should be made to other data handling and measurement er
35、ror modelling techniques. Although these techniques are referred to, they are not specified in ISO 8196|IDF 128 (all parts). BS ISO 8196-2:2009 INTERNATIONAL STANDARD ISO 8196-2:2009(E) IDF 128-2:2009(E) ISO and IDF 2009 All rights reserved 1Milk Definition and evaluation of the overall accuracy of
36、alternative methods of milk analysis Part 2: Calibration and quality control in the dairy laboratory 1 Scope This part of ISO 8196|IDF 128 gives guidelines for the calibration of instruments and quality control procedures for milk analysis in dairy laboratories. 2 Normative references The following
37、referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 8196-1|IDF 128-1:2009, Milk Definition and evaluation of th
38、e overall accuracy of alternative methods of milk analysis ISO 8196-3|IDF 128-3:2009, Milk Definition and evaluation of the overall accuracy of alternative methods of milk analysis Part 3: Protocol for the evaluation and validation of alternative quantitative methods of milk analysis 3 Terms, defini
39、tions, and symbols 3.1 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 8196-1|IDF 128-1 and the following apply. 3.1.1 standardization of an instrument experimental evaluation of the exactness of the calibration of an instrument by reference to the tru
40、e values given either by a reference method or by standard materials or a standard instrument 3.1.2 calibration of an instrument adjustment of the signal from an instrument so that, at each level of the component, the mean of individual test results given by the instrument closely approximates the t
41、rue value of the component concentration IMPORTANT Even if the term “calibration” is often used for both the standardization and calibration of instruments (see Clause 4), the use of these words according to the definitions in 3.1.1 and 3.1.2 is strongly recommended. BS ISO 8196-2:2009 ISO 8196-2:20
42、09(E) IDF 128-2:2009(E) 2 ISO and IDF 2009 All rights reserved3.2 Symbols b linear regression coefficient or slope d average of differences d ior mean bias d idifference between means of duplicates of x iand y irel d relative mean bias d L limit of the mean bias d rel d L limit of the relative mean
43、bias m 0reference value for the control chart n number of replicates P xysum of products of x and y q number of samples r repeatability limit r xycorrelation coefficient R reproducibility limit S dsum of squares of d S xsum of squares of x S ysum of squares of y s bstandard deviation of slope s x 0s
44、tandard error of estimate x 0s yestimate of standard deviation of y s yxestimate of the standard deviation of accuracy t obsobserved value of the Student t-test t 1 /2t-value of the Student distribution for a two-sided probability 1 t 1 t-value of the Student distribution for a one-sided probability
45、 1 u 1 /2value of the standard normal distribution for a two-sided probability 1 x arithmetic average of i x i x mean of duplicates of x iy arithmetic average of i y i y mean of duplicates of y i() yx predicted values from x by linear regression. degree of freedom rstandard deviation of repeatabilit
46、y Rstandard deviation of reproducibility ystandard deviation of y yxstandard deviation of accuracy yxrelrelative standard deviation of accuracy BS ISO 8196-2:2009 ISO 8196-2:2009(E) IDF 128-2:2009(E) ISO and IDF 2009 All rights reserved 34 Calibration of instruments 4.1 General principles This claus
47、e only considers the general principles of calibration which apply to any alternative method of milk analysis. Detailed and specific instructions for the calibration procedure, as well as for the preliminary checks concerning each group of methods, shall be given in specific documentation. The calib
48、ration here described is based on the assumption of an existing linear relationship between the alternative method and the reference method. The utilization of an ordinary least-squares (OLS) linear regression model with the reference method as dependent variable (y-axis) is recommended as practical
49、 and reliable: a) the measured residual standard deviation is structurally the lowest and is independent of the exactness of calibration, hence it can be used for calibration control as a method accuracy characteristic (see ISO 8196-1|IDF 128-1); b) prediction of true values from alternative method values and calculation of associated errors is simplified; c) the differences in measurement results as compared to applying other linear regression models are not significant
