1、BRITISH STANDARD Milk and milk products Determination of nitrogen content Routine method using combustion according to the Dumas principle The European Standard EN IS0 14891:2002 has the status ofa British Standard ICs 67.100.01 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW
2、BS EN IS0 14891 :2002 Incovorating Corrigendum No. I BS EN IS0 14891:2002 Amd.No. National foreword Date Comments This British Standard is the official English language version of EN IS0 14891:2002. It is identical with IS0 14891:2002. The UKparticipation in its preparation was entrusted to Technica
3、l Committee AW/5, Milk and milk products, which has the responsibility to: 13914 Corrigendum No. 1 - - aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; m
4、onitor related international and European developments and promulgate them in the UK. - A list of organizations represented on this committee can be obtained on request to its secretary. Cros s-r e ferenc es The British Standards which implement international or European publications referred to in
5、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 provisions of a contract. U
6、sers of British Standards are responsible for their correct application. Compliance with a British Standard does not ofitself confer immunity from legal obligations. 10 May 2002 Incorporating the Annex ZA Summary of pages This document comprises a front cover, an inside front cover, the EN IS0 title
7、 page, the EN IS0 foreword page, the IS0 title page, pages ii tov, a blank page, pages 1 to 14, the Annex ZA page and a back cover. This British Standard. having - been prepared under the The BSI copyright date displayed in this document indicates when the document was last issued. direction of the
8、Consumer Products and Services Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 28 March 2002 O BSI 10 May 2002 ISBN O 580 39263 5 EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN IS0 14891 March 2002 ICs 67.100.01 English
9、version Milk and milk products - Determination of nitrogen content - Routine method using combustion according to the Dumas principle (IS0 14891 :2002) Lait et produits laitiers - Dtermination de la teneur en azote - Mthode pratique par combustion selon le principe de Dumas (IS0 14891:2002) Milch un
10、d Milchprodukte - Bestimmung des Stickstoffgehaltes - Verbrennungsverfahren nach Dumas (Routineverfahren) (IS0 14891:2002) This European Standard was approved by CEN on 1 March 2002 CEN members are bound to comply with the CENKENELEC Internal Regulations which stipulate the conditions for giving thi
11、s European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Management Centre or to any CEN member. This European Standard exists in three official versions (Eng
12、lish, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Czech Repub
13、lic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION EUROPISCHES KOMITEE FR NORMUNG COMIT EUROPEN DE NORMALISATION Management Centre: rue de Sta
14、ssart, 36 B-1050 Brussels O 2002 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN IS0 14891:2002 E EN IS0 14891:2002 I CORRECTED 2002-04-17 I Foreword This document (IS0 14891 :2002) has been prepared by Technical Committee ISO/TC 3
15、4 “Agricultural food products“ in collaboration with Technical 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 tex
16、t or by endorsement, at the latest by September 2002, and conflicting national standards shall be withdrawn at the latest by September 2002. According to the CENKENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard
17、: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of the International Standard IS0 14891:2002 has been approved by C
18、EN as a European Standard without any modifications. NOTE Normative references to International Standards are listed in annex ZA (normative). INTERNATIONAL STANDARD IS0 14891 IDF 185 First edition 2002-03-01 Milk and milk products - Determination of nitrogen content - Routine method using combustion
19、 according to the Dumas principle Laif ef produifs laifiers - Dferminafion de la feneur en azofe - Mfhode prafique par combusfion selon le principe de Dumas Reference num bers IS0 14891 :2002(E) IDF 185:2002(E) EN IS0 14891:2002 Icsid FDParemi ihTs PDF file rnac ytnoaie nrnt deddebyfepca.se In ccaoc
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21、s licnesilop gnic.y ieNtt rehl ehStneC Olar Secrteiraat t ron1 ehDca Fcetps any ailbytili ni htsi area. Ai ebods a tredarnafo kr Aebod Systernl sncotaropr.de teDails fo ts ehoftwaorp ercudts ust deo crtaet ehis PDF file ceb na fi dnuon tlareneG eh Info leratit evo tf ehile; tP ehD-Fcrtaeiarap nornte
22、sre were tpoirniz deoirp rnti.gn Evc yreasah er t neebakt neo snet erutah tf ehile is suitlbae fosu rl yb eSO rnernidob rebse I dnaDF tanilano cornrnitt.seel n thlnu eikletneve yi htalborp a rneler atit gnoi ti sf o,dnu plsaei enfornrt hl eStneC OlarS ecrteiraata tt hrdda esesg leb nevow. II EN IS0
23、14891:2002 Contents Page Foreword iv. vi 1 Scope 1 2 Normative reference 1 3 Term and definition . 1 4 Principle 1 . 5 Reagents 1 Sampling . 3 6 Apparatus . 2 7 8 Preparation of test sample 3 8.1 General 3 8.2 Liquid test samples . 3 9 Procedure 4 9.1 General 4 9.2 Test portion 4 9.3 Control of oxyg
24、en demand . 4 9.4 Calibration 4 9.5 Determination . 4 9.6 Detection and integration . 5 10 Calculation and expression of results 5 10.1 Calculation 5 10.2 Expression of results 5 11 Precision . 6 11 . 1 Interlaboratory test 6 11.2 Repeatability 6 12 Test report 7 Annex A (informative) Flowchart for
25、the basic design of a Dumas apparatus . 8 Annex B (informative) Schemes of suitable types of Dumas apparatus . 9 11 11.3 Reproducibility 7 Annex C (informative) Equipment calibration Annex D (informative) Comparison of results using the Dumas method with those obtained by the Kjeldahl method . 13 Bi
26、bliography 14 . 111 EN IS0 14891:2002 Foreword IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 technical committees. Each member body
27、 interested in a subject 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. IS0 collaborates closely with the International Electrotec
28、hnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISOAEC Directives, Part 3. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by t
29、he technical committees 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 International Standard may be the subject o
30、f patent rights. IS0 shall not be held responsible for identifying any or all such patent rights. International Standard IS0 14891 IDF 185 was prepared by Technical Committee ISO/TC 34, Food producfs, Subcommittee SC 5, Milk and milk producfs, and the International Dairy Federation (IDF), in collabo
31、ration with AOAC International. It is being published jointly by IS0 and IDF and separately by AOAC International. Annexes A, B, C and D are for information only. iv EN IS0 14891:2002 Foreword IDF (the International Dairy Federation) is a worldwide federation of the dairy sector with a National Comm
32、ittee 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 IS0 and AOAC International in the development of standard methods of analysis and sampling for milk and milk products. Draft I
33、nternational 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. International Standard IS0 14891/IDF 185 was prepared by
34、 Technical Committee ISO/TC 34, Food producfs, Subcommittee SC 5, Milk and milk producfs, and the International Dairy Federation (IDF), in collaboration with AOAC International. It is being published jointly by IS0 and IDF and separately by AOAC International. All work was carried out by the Joint I
35、SO/IDF/AOAC Action Team, Nifrogen compounds, of the Standing Committee, Main compounds ofmilk, under the aegis of its project leader, Prof. H. Frister (DE). V EN IS0 14891:2002 EN IS0 14891:2002 Milk and milk products - Determination of nitrogen content - Routine method using combustion according to
36、 the Dumas principle 1 Scope This International Standard specifies a routine method for the determination of the total nitrogen content of milk and milk products. 2 Normative reference The following normative document contains provisions which, through reference in this text, constitute provisions o
37、f this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent edition of the normati
38、ve document indicated below. For undated references, the latest edition of the normative document referred to applies. Members of IS0 and IEC maintain registers of currently valid International Standards. IS0 8968-1 IDF 20-1, Milk - Deferminafion of nifrogen confenf - Par 1: Kjeldahl mefhod 3 Term a
39、nd definition For the purposes of this International Standard, the following term and definition apply. 3.1 nitrogen content mass fraction of the total nitrogen determined by the procedure specified in this International Standard NOTE The nitrogen content is expressed as a percentage by mass. 4 Prin
40、ciple A test portion is heated to destruction in a combustion tube at high temperature (900 OC to 1 200 OC) in an oxygen atmosphere according to the Dumas principle. All interfering components are removed from the resulting gas mixture. The nitrogen compounds in the test portion are converted to mol
41、ecular nitrogen, followed by quantitative determination using a thermal conductivity detector. The nitrogen content is calculated using a microprocessor. 5 Reagents Use only reagents of recognized analytical grade, or reagents of equivalent purity as specified by instrument manufacturers. 5.1 Carrie
42、r gases: use one of the following. 1 EN IS0 14891:2002 5.1.1 99,995 % (volume fraction) for samples with low nitrogen contents. Carbon dioxide (CO,), purity 99,9 % (volume fraction) for samples with moderate nitrogen contents; 5.1.2 5.2 Helium (He), purity 99,996 % (volume fraction). Oxygen (O,), pu
43、rity 99,995 % (volume fraction). 5.3 5.4 Platinum catalyst (5 % of Pt on AI,O,) is blended with Cu0 at a ratio of 1 to 7, 8 or 9 parts. To prevent separation as result of the different bulk densities of the two materials, it is not recommended to prepare the mixture before filling the tube. It is ad
44、visable to pour the platinum catalyst and copper oxide simultaneously into the post-combustion tube using a suitable funnel. 5.5 Silver wool. Absorbent for SO, e.g. lead chromate to eliminate any sulfur compounds from the combustion products. Copper oxide platinum catalyst (as filling material for t
45、he post-combustion tube). Silver wool should be desegregated before being inserted in the post-combustion or reduction tube. 5.6 Silica (quartz) or glass wool. 5.7 Copper or tungsten (wire, cuttings or powder), suitable for filling the reduction tube. To improve the precision of analytical results f
46、or low nitrogen contents, the use of copper or tungsten wire is recommended. 5.8 support material, to fill the drying tubes. Phosphorus pentoxide (P205) or granulated magnesium perchlorate Mg(CIO,), or another suitable 5.9 Hollow corundum spheres or aluminium oxide pellets, suitable for filling the
47、combustion tube. 5.10 Copper oxide (CuO), suitable as a filling material for the combustion tube. 5.1 1 Sodium hydroxide (NaOH), on a support material. 5.12 Standard nitrogen compounds, e.g. aspartic acid (C,H,NO,), ethylenediaminetetraacetic acid (Cl,Hl,N,O,) (see annex C), or other suitable refere
48、nce reagents with known constant nitrogen content (e.g. urea, tyrosine, phenylalanine); minimum assay should be 99 %. For calibration purposes (see 9.4), use a standard nitrogen compound to prepare a standard series with a nitrogen content of 4 mg to 100 mg in equal steps of about 5 mg nitrogen. Pre
49、pare a second standard series with a nitrogen content of 10 mg to 200 mg in equal steps of about 10 mg nitrogen. 6 Apparatus Usual laboratory equipment and, in particular, the following. 6.1 Analytical balance, capable of weighing to 0,000 1 g. 6.2 Drying oven, capable of maintaining a temperature of between 105 OC and 110 OC. 6.3 Crucibles, e.g. made of stainless steel or ceramic, or tin capsules, suitable for the Dumas apparatus used. NOTE 1 Several commercial instruments are provided with an automatic sampler. NOTE 2 Some solid samples (e.g. powders) can be pressed to for
