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1、BRITISH STANDARD BS EN ISO 8968-4:2002 Incorporating Corrigendum No. 1 Milk Determination of nitrogen content Part 4: Determination of non-protein nitrogen content The European Standard EN ISO 8968-4:2001 has the status of a British Standard ICS 67.100.10 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS
2、PERMITTED BY COPYRIGHT LAW Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 15:26:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN ISO 8968-4:2002 This British Standard, having been prepared under the direction of the Consumer Products and Services Sector Policy and Strategy Committee, was
3、published under the authority of the Standards Policy and Strategy Committee on 28 January 2002 BSI 2 April 2002 ISBN 0 580 38872 7 National foreword This British Standard is the official English language version of EN ISO 8968-4:2001. It is identical with ISO 8968-4:2001. The UK participation in it
4、s preparation was entrusted to Technical Committee AW/5, Milk and milk products, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European public
5、ations referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provi
6、sions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries
7、 on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN ISO title page, the EN ISO foreword page,
8、the ISO title page, pages ii to v, a blank page, pages 1 to 6, the Annex ZA page and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. DateComments 13823 Corrigendum No. 1 2 April 2002Incorporatin
9、g Annex ZA Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 15:26:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 8968-4 December 2001 ICS 67.100.10 English version Milk - Determination of nitrogen content - Part 4: Determination of non-pr
10、otein nitrogen content (ISO 8968-4:2001) Lait - Dtermination de la teneur en azote - Partie 4: Dtermination de la teneur en azote non protique (ISO 8968-4:2001) Milch - Bestimmung des Stickstoffgehaltes - Teil 4: Bestimmung des Nichtproteinstickstoff-Gehaltes (ISO 8968-4:2001) This European Standard
11、 was approved by CEN on 15 December 2001. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning su
12、ch national standards may be obtained on application to the Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language a
13、nd notified to the Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerl
14、and and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: rue de Stassart, 36 B-1050 Brussels 2001 CENAll rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN
15、 ISO 8968-4:2001 E Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 15:26:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI CORRECTED 2002-03-13 Foreword This document (ISO 8968-4:2001) has been prepared by Technical Committee ISO/TC 34 “Agricultural food products“ in collaboration with Technical
16、Committee CEN/TC 302 “Milk and milk products - Methods of sampling and analysis“, the secretariat of which is held by NEN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by June 2002, and conflictin
17、g national standards shall be withdrawn at the latest by June 2002. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, G
18、reece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of the International Standard ISO 8968-4:2001 has been approved by CEN as a European Standard without any modifications. NOTE Normative references
19、 to International Standards are listed in annex ZA (normative). EN ISO 89684:2001 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 15:26:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Reference numbers ISO 8968-4:2001(E) IDF 20-4:2001(E) INTERNATIONAL STANDARD ISO 8968-4 IDF 20-4 First edition
20、2001-12-15 Milk Determination of nitrogen content Part 4: Determination of non-protein-nitrogen content Lait Dtermination de la teneur en azote Partie 4: Dtermination de la teneur en azote non protique EN ISO 89684:2001 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 15:26:08 GMT+00:00 2006,
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24、ttahlborp a meler ati gnto it is f,dnuo plsae einfomr t ehIStneC Olar Secrteiraatta trdda ehsesig leb nevow. ii EN ISO 89684:2001 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 15:26:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS-8698 O4:(1002)E ID-02 F4:(1002E) iii Contents Page Foreword.
25、iv 1 Scope1 2 Normative references1 3 Term and definition .1 4 Principle1 5 Reagents.2 6 Apparatus.2 7 Sampling.3 8 Preparation of test sample3 9 Procedure.3 9.1 Test portion3 9.2 Determination.3 9.3 Blank test4 10 Calculation and expression of results.4 11 Precision.5 11.1 Interlaboratory test5 11.
26、2 Repeatability 5 11.3 Reproducibility.5 12 Test report5 Bibliography6 EN ISO 89684:2001 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 15:26:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS-8698 O4:(1002)E ID-02 F4:(1002E) iv Foreword ISO (the International Organization for Standardization)
27、 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 subject for which a technical committee has been established has the right to be repre
28、sented 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) on all matters of electrotechnical standardization. International Standards are
29、 drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an Internationa
30、l 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 part of ISO 8968IDF 20 may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Inte
31、rnational Standard ISO 8968-4IDF 20-4 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF), in collaboration with AOAC International. It is being published jointly by ISO and IDF and separately by AOAC I
32、nternational. ISO 8968IDF 20 consists of the following parts, under the general title Milk Determination of nitrogen content: Part 1: Kjeldahl method Part 2: Block-digestion method (Macro method) Part 3: Block-digestion method (Semi-micro rapid routine method) Part 4: Determination of the non-protei
33、n-nitrogen content Part 5: Determination of the protein-nitrogen content EN ISO 89684:2001 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 15:26:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS-8698 O4:(1002)E ID-02 F4:(1002E) v Foreword IDF (the International Dairy Federation) is a worldwide
34、 federation of the dairy sector with a National Committee in every member country. Every National Committee has the right to be represented on the IDF Standing Committees carrying out the technical work. IDF collaborates with ISO and AOAC International in the development of standard methods of analy
35、sis and sampling for milk and milk products. Draft 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 National Committees casting a vote. Inte
36、rnational Standard ISO 8968-4IDF 20-4 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF), in collaboration with AOAC International. It is being published jointly by ISO and IDF and separately by AOAC I
37、nternational. All work was carried out by the Joint ISO/IDF/AOAC Action Team, Nitrogen compounds, under the aegis of its project leader, Mr D.M. Barbano (US). EN ISO 89684:2001 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 15:26:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN ISO 89684:200
38、1 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 15:26:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI INTERNATNOIAL STANDARD IS-8698 O4:(1002)E ID-02 F4:(1002E) 1 Milk Determination of nitrogen content Part 4: Determination of non-protein-nitrogen content WARNING The use of this part of ISO 8
39、968 IDF 20 may involve the use of hazardous materials, operations, and equipment. This standard does not purport to address all the safety risks associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and healthy practices and determine the appl
40、icability of local regulatory limitations prior to use. 1 Scope This part of ISO 8968IDF 20 specifies a method for the determination of the non-protein nitrogen content of liquid milk, whole or skimmed. 2 Normative references The following normative documents contain provisions which, through refere
41、nce in this text, constitute provisions of this part of ISO 8968IDF 20. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this part of ISO 8968IDF 20 are encouraged to investigate the possibility of applyi
42、ng the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 8968-1IDF 20-1:2001, Milk Determination of nitro
43、gen content Part 1: Kjeldahl method ISO 8968-2IDF 20-2:2001, Milk Determination of nitrogen content Part 2: Block-digestion method (Macro method) 3 Term and definition For the purposes of this part of ISO 8968IDF 20, the following term and definition apply. 3.1 non-protein-nitrogen content mass frac
44、tion of substances determined by the procedure specified in this part of ISO 8968IDF 20 NOTE The non-protein-nitrogen content is expressed as a percentage by mass. 4 Principle Protein is precipitated from a test portion by the addition of trichloroacetic acid solution such that the final concentrati
45、on of trichloroacetic acid in the mixture is approximately 12 %. The precipitated milk protein is removed by filtration, and the remaining filtrate contains the non-protein-nitrogen components. The nitrogen content of the filtrate is determined by the procedure described either in part 1 or part 2 o
46、f ISO 8968IDF 20. EN ISO 89684:2001 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 15:26:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS-8698 O4:(1002)E ID-02 F4:(1002E) 2 NOTE Where the total nitrogen content of the milk sample has previously been determined, the true protein-nitrogen cont
47、ent can be calculated as the difference between the total nitrogen content and the non-protein-nitrogen content. 5 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized water or water of equivalent purity. The reagents are as specified
48、for the determination of total nitrogen by the method described either in part 1 or part 2 of ISO 8968IDF 20, together with the following. A laboratory may decide whether to use the method described in part 1 or part 2 of ISO 8968IDF 20. 5.1 Trichloroacetic acid solution (CCl3COOH) Dissolve 15,0 g o
49、f trichloroacetic acid in water in a 100 ml one-mark volumetric flask. Dilute to the mark with water. Do not use concentrations of trichloroacetic acid and volumes of solutions other than those specified. The performance of the method with respect to mean value and between-laboratory performance characteristics will differ if other than the specified concentrations of trichloroacetic acid and volumes of solutions are used. 5.2 Hydrochloric acid standard volumetric solution, c(HCl) = (0,01 0,000 1) mol/l.