1、BRITISH STANDARD BS EN ISO 14891:2002 Incorporating Corrigendum No. 1 Milk and milk products Determination of nitrogen content Routine method using combustion according to the Dumas principle The European Standard EN ISO 14891:2002 has the status of a British Standard ICS 67.100.01 NO COPYING WITHOU
2、T BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBS EN ISO 14891:2002 This British Standard, having been prepared under the direction of the Consumer Products and Services Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 28
3、 March 2002 BSI 10 May 2002 ISBN 0 580 39263 5 National foreword This British Standard is the official English language version of EN ISO 14891:2002. It is identical with ISO 14891:2002. The UK participation in its preparation was entrusted to Technical Committee AW/5, Milk and milk products, which
4、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 publications referred to in this document may be found in the BSI Standards Catalogue under t
5、he 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. Users of British Standards are responsible for their correct appli
6、cation. 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 on the interpretation, or proposals for change, and keep the UK interests informed; mo
7、nitor 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, the ISO title page, pages ii to v, a blank page, pages 1 to 14, the Annex ZA page and a
8、 back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date Comments 13914 Corrigendum No. 1 10 May 2002 Incorporating the Annex ZAEUROPEANSTANDARD NORMEEUROPENNE EUROPISCHENORM ENISO14891 March2002 ICS
9、67.100.01 Englishversion MilkandmilkproductsDeterminationofnitrogencontent RoutinemethodusingcombustionaccordingtotheDumas principle(ISO14891:2002) LaitetproduitslaitiersDterminationdelateneuren azoteMthodepratiqueparcombustionselonleprincipe deDumas(ISO14891:2002) MilchundMilchprodukteBestimmungdes
10、 StickstoffgehaltesVerbrennungsverfahrennachDumas (Routineverfahren)(ISO14891:2002) ThisEuropeanStandardwasapprovedbyCENon1March2002. CENmembersareboundtocomplywiththeCEN/CENELECInternalRegulationswhichstipulatetheconditionsforgivingthisEurope an Standardthestatusofanationalstandardwithoutanyalterat
11、ion.Uptodatelistsandbibliographicalreferencesconcernings uchnational standardsmaybeobtainedonapplicationtotheManagementCentreortoanyCENmember. ThisEuropeanStandardexistsinthreeofficialversions(English,French,German).Aversioninanyotherlanguagemadebytra nslation undertheresponsibilityofaCENmemberintoi
12、tsownlanguageandnotifiedtotheManagementCentrehasthesamestatusasthe official versions. CENmembersarethenationalstandardsbodiesofAustria,Belgium,CzechRepublic,Denmark,Finland,France,Germany,Greece, Iceland,Ireland,Italy,Luxembourg,Malta,Netherlands,Norway,Portugal,Spain,Sweden,SwitzerlandandUnitedKing
13、dom. EUROPEANCOMMITTEEFORSTANDARDIZATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2002CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwideforCENnationalMembers. Ref.No.ENISO14891:2002EINESO41:198200(2E) 2 CORRECTED20020417
14、Foreword Thisdocument(ISO14891:2002)hasbeenpreparedbyTechnicalCommitteeISO/TC34 “Agriculturalfoodproducts“incollaborationwithTechnicalCommitteeCEN/TC302“Milkand milkproductsMethodsofsamplingandanalysis“,thesecretariatofwhichisheldbyNEN. ThisEuropeanStandardshallbegiventhestatusofanationalstandard,ei
15、therbypublication ofanidenticaltextorbyendorsement,atthelatestbySeptember2002,andconflicting nationalstandardsshallbewithdrawnatthelatestbySeptember2002. AccordingtotheCEN/CENELECInternalRegulations,thenationalstandardsorganizationsof thefollowingcountriesareboundtoimplementthisEuropeanStandard:Aust
16、ria,Belgium, CzechRepublic,Denmark,Finland,France,Germany,Greece,Iceland,Ireland,Italy, Luxembourg,Malta,Netherlands,Norway,Portugal,Spain,Sweden,Switzerlandandthe UnitedKingdom. Endorsementnotice ThetextoftheInternationalStandardISO14891:2002hasbeenapprovedbyCENasa EuropeanStandardwithoutanymodific
17、ations. NOTENormativereferencestoInternationalStandardsarelistedinannexZA(normative). ENISO14891:2002 Reference numbers ISO 14891:2002(E) IDF 185:2002(E)INTERNATIONAL STANDARD ISO 14891 IDF 185 First edition 2002-03-01 Milk and milk products Determination of nitrogen content Routine method using com
18、bustion according to the Dumas principle Lait et produits laitiers Dtermination de la teneur en azote Mthode pratique par combustion selon le principe de Dumas lcsid FDParemi ihTs PDF file mac ytnoaie nmt deddebyfepca.se In ccaocnadrw eith Aebods licsneilop gnic,y this file mairp eb yntiv ro deewb d
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20、 any ailbytili ni htsi area. Ai ebods a tredamafo kr Aebod SystemI 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 nomtesre were tpoimizf deoirp rnti.gn Evc yreasah er t neebakt neo snet erutah tf e
21、hile is suitlbae fosu rI yb eSO memidob rebse I dnaDF tanilano committ.seeI n thlnu eikletneve yt htalborp a meler atit gnoi ti sf o,dnu plsaei enfomrt hI eStneC OlarS ecrteiraata tt hrdda esesg ileb nevow. ii ENISO14891:2002 iiiContents Page Forewordiv, vi 1 Scope 1 2 Normative reference1 3 Term an
22、d definition .1 4 Principle1 5 Reagents.1 6 Apparatus .2 7 Sampling.3 8 Preparation of test sample3 8.1 General3 8.2 Liquid test samples .3 9 Procedure .4 9.1 General4 9.2 Test portion 4 9.3 Control of oxygen demand .4 9.4 Calibration 4 9.5 Determination.4 9.6 Detection and integration .5 10 Calcula
23、tion and expression of results.5 10.1 Calculation .5 10.2 Expression of results 5 11 Precision.6 11.1 Interlaboratory test6 11.2 Repeatability 6 11.3 Reproducibility.7 12 Test report 7 Annex A (informative) Flowchart for the basic design of a Dumas apparatus.8 Annex B (informative) Schemes of suitab
24、le types of Dumas apparatus.9 Annex C (informative) Equipment calibration 11 Annex D (informative) Comparison of results using the Dumas method with those obtained by the Kjeldahl method.13 Bibliography14 ENISO14891:2002iv Foreword ISO (the International Organization for Standardization) is a worldw
25、ide 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 represented on th
26、at 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 drafted in
27、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 International Standard r
28、equires 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 of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. International St
29、andard ISO 14891 IDF 185 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 International.
30、 Annexes A, B, C and D are for information only. ENISO14891:2002 vForeword IDF (the International Dairy Federation) is a worldwide 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
31、 carrying out the technical work. IDF collaborates with ISO and AOAC International in the development of standard methods of analysis and sampling for milk and milk products. Draft International Standards adopted by the Action Teams and Standing Committees are circulated to the National Committees f
32、or voting. Publication as an International Standard requires approval by at least 50 % of National Committees casting a vote. International Standard ISO 14891/IDF 185 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy
33、Federation (IDF), in collaboration with AOAC International. It is being published jointly by ISO and IDF and separately by AOAC International. All work was carried out by the Joint ISO/IDF/AOAC Action Team, Nitrogen compounds, of the Standing Committee, Main compounds of milk, under the aegis of its
34、 project leader, Prof. H. Frister (DE). ENISO14891:2002ENISO14891:2002 1Milk and milk products Determination of nitrogen content Routine method using combustion according to the Dumas principle 1 Scope This International Standard specifies a routine method for the determination of the total nitrogen
35、 content of milk and milk products. 2 Normative reference The following normative document contains provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do no
36、t apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent edition of the normative document indicated below. For undated references, the latest edition of the normative document referred to applies. Members
37、of ISO and IEC maintain registers of currently valid International Standards. ISO 8968-1 IDF 20-1, Milk Determination of nitrogen content Part 1: Kjeldahl method 3 Term and definition For the purposes of this International Standard, the following term and definition apply. 3.1 nitrogen content mass
38、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 Principle A test portion is heated to destruction in a combustion tube at high temperature (900 C to 1 200 C) in an oxygen atmosphere
39、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 molecular nitrogen, followed by quantitative determination using a thermal conductivity detector. The nitrogen content is calculated us
40、ing a microprocessor. 5 Reagents Use only reagents of recognized analytical grade, or reagents of equivalent purity as specified by instrument manufacturers. 5.1 Carrier gases: use one of the following. ENISO14891:20022 5.1.1 Carbon dioxide (CO 2 ), purity 99,9 % (volume fraction) for samples with m
41、oderate nitrogen contents; 99,995 % (volume fraction) for samples with low nitrogen contents. 5.1.2 Helium (He), purity 99,996 % (volume fraction). 5.2 Oxygen (O 2 ), purity 99,995 % (volume fraction). 5.3 Absorbent for SO 2 , e.g. lead chromate to eliminate any sulfur compounds from the combustion
42、products. 5.4 Copper oxide platinum catalyst (as filling material for the post-combustion tube). Platinum catalyst (5 % of Pt on Al 2 O 3 ) is blended with CuO 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 recommen
43、ded to prepare the mixture before filling the tube. It is advisable to pour the platinum catalyst and copper oxide simultaneously into the post-combustion tube using a suitable funnel. 5.5 Silver wool. Silver wool should be desegregated before being inserted in the post-combustion or reduction tube.
44、 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 for low nitrogen contents, the use of copper or tungsten wire is recommended. 5.8 Phosphorus pentoxide (P 2 O 5 ) or granulat
45、ed magnesium perchlorate Mg(ClO 4 ) 2 , or another suitable support material, to fill the drying tubes. 5.9 Hollow corundum spheres or aluminium oxide pellets, suitable for filling the combustion tube. 5.10 Copper oxide (CuO), suitable as a filling material for the combustion tube. 5.11 Sodium hydro
46、xide (NaOH), on a support material. 5.12 Standard nitrogen compounds, e.g. aspartic acid (C 4 H 7 NO 4 ), ethylenediaminetetraacetic acid (C 10 H 16 N 2 O 8 ) (see annex C), or other suitable reference reagents with known constant nitrogen content (e.g. urea, tyrosine, phenylalanine); minimum assay
47、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. Prepare a second standard series with a nitrogen content of 10 mg to 200 mg in equal steps of about 10 mg
48、 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 C and 110 C. 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.
