BS EN ISO 5983-2-2009 Animal feeding stuffs - Determination of nitrogen content and calculation of crude protein content - Part 2 Block digestion and steam distillation method (ISO.pdf

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1、BS EN ISO5983-2:2009ICS 65.120NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDAnimal feeding stuffs Determination ofnitrogen content andcalculation of crudeprotein contentPart 2: Block digestion and steamdistillation method (ISO 5983-2:2009)This British Standard

2、was published under theauthority of the StandardsPolicy and StrategyCommittee on 3 July2009. BSI 2009ISBN 978 0 580 66817 3Amendments/corrigenda issued since publicationDate CommentsBS EN ISO 5983-2:2009National forewordThis British Standard is the UK implementation of EN ISO 5983-2:2009. It superse

3、des BS EN ISO 5983-2:2005which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee AW/10, Animal feeding stuffs.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the n

4、ecessary provisionsof a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.1EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 5983-2June 2009ICS 65.120 Supersedes EN ISO 5983-2:2005 English VersionAnimal fee

5、ding stuffs - Determination of nitrogen content andcalculation of crude protein content - Part 2: Block digestion andsteam distillation method (ISO 5983-2:2009)Aliments des animaux - Dosage de lazote et calcul de lateneur en protines brutes - Partie 2: Mthode de digestionen bloc et distillation la v

6、apeur (ISO 5983-2:2009)Futtermittel - Bestimmung des Stickstoffgehaltes undBerechnung des Rohproteingehaltes - Teil 2:Blockaufschluss- und Dampfdestillationsverfahren (ISO5983-2:2009)This European Standard was approved by CEN on 30 May 2009.CEN members are bound to comply with the CEN/CENELEC Intern

7、al Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.

8、This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are

9、the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerlan

10、d and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: Avenue Marnix 17, B-1000 Brussels 2009 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 5983

11、-2:2009: EBS EN ISO 5983-2:2009EN ISO 5983-2:2009 (E) 3 Foreword This document (EN ISO 5983-2:2009) has been prepared by Technical Committee ISO/TC 34 “Food products“ in collaboration with Technical Committee CEN/TC 327 “Animal feeding stuffs - Methods of sampling and analysis”, the secretariat of w

12、hich 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 December 2009, and conflicting national standards shall be withdrawn at the latest by December 2009. Attention is drawn to the

13、possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. This document supersedes EN ISO 5983-2:2005. According to the CEN/CENELEC Internal Regulations, the national sta

14、ndards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,

15、Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 5983-2:2009 has been approved by CEN as a EN ISO 5983-2:2009 without any modification. BS EN ISO 5983-2:2009ISO 5983-2:2009(E) ISO 2009 All rights reserved iiiContents Page Fo

16、reword iv 1 Scope . 1 2 Normative references . 1 3 Terms and definitions. 2 4 Principle. 2 5 Reagents 2 6 Apparatus 4 7 Sampling 4 8 Preparation of test sample. 5 9 Procedure 5 9.1 General. 5 9.2 Test portion . 5 9.3 Determination 5 9.4 Blank test. 6 9.5 Recovery tests 7 10 Calculation and expressio

17、n of results 7 10.1 Calculation. 7 10.2 Calculation of crude protein content 8 10.3 Expression of crude protein content results .8 11 Precision 8 11.1 Interlaboratory tests . 8 11.2 Repeatability 9 11.3 Reproducibility 9 12 Test report . 9 Annex A (informative) Results of interlaboratory tests 10 An

18、nex B (informative) Results of a profiency test; comparison of the colorimetric and potentiometric endpoint determination of the titration 14 Bibliography . 15 BS EN ISO 5983-2:2009ISO 5983-2:2009(E) iv ISO 2009 All rights reservedForeword ISO (the International Organization for Standardization) is

19、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 represent

20、ed 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 dra

21、fted 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 committees are circulated to the member bodies for voting. Publication as an International St

22、andard 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 held responsible for identifying any or all such patent rights. ISO 5983-2 was prepare

23、d by Technical Committee ISO/TC 34, Food products, Subcommittee SC 10, Animal feeding stuffs. This second edition cancels and replaces the first edition (ISO 5983-2:2005), which has been technically revised. ISO 5983 consists of the following parts, under the general title Animal feeding stuffs Dete

24、rmination of nitrogen content and calculation of crude protein content: Part 1: Kjeldahl method Part 2: Block digestion and steam distillation method BS EN ISO 5983-2:2009INTERNATIONAL STANDARD ISO 5983-2:2009(E) ISO 2009 All rights reserved 1Animal feeding stuffs Determination of nitrogen content a

25、nd calculation of crude protein content Part 2: Block digestion and steam distillation method WARNING The use of this method may involve the use of hazardous materials, operations and equipment. This part of ISO 5983 does not purport to address all the safety risks associated with its use. It is the

26、 responsibility of the user of this method to establish appropriate health and safety practices and determine the applicability of local regulatory limitations prior to use. 1 Scope This part of ISO 5983 specifies a method for the determination of nitrogen content of animal feeding stuffs according

27、to the Kjeldahl method, and a method for the calculation of the crude protein content. It is suitable for use as a semi-micro rapid routine method using block digestion, copper catalyst, and steam distillation into boric acid. The method is applicable to the determination of greater than 0,5 % mass

28、fraction Kjeldahl nitrogen in animal feeding stuffs, pet foods, and their raw materials. The method does not measure oxidized forms of nitrogen nor heterocyclic nitrogen compounds. The method does not distinguish between protein nitrogen and non-protein nitrogen. NOTE If it is of importance to deter

29、mine the content of non-protein nitrogen, an appropriate method can be used. 2 Normative references The following 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 refer

30、red document (including any amendments) applies. ISO 1871, Food and feed products General guidelines for the determination of nitrogen by the Kjeldahl method ISO 6498, Animal feeding stuffs Guidelines for sample preparation 1)1) To be published. (Revision of ISO 6498:1998) BS EN ISO 5983-2:2009ISO 5

31、983-2:2009(E) 2 ISO 2009 All rights reserved3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 nitrogen content mass fraction of nitrogen determined by the procedure specified in this part of ISO 5983 NOTE The nitrogen content is expressed as a

32、percentage mass fraction or in grams per kilogram. 3.2 crude protein content nitrogen content (3.1) as a mass fraction multiplied by the factor 6,25 NOTE The crude protein content is expressed as a percentage mass fraction or in grams per kilogram. 4 Principle The test portion is digested using a bl

33、ock digestion or equivalent apparatus. Concentrated sulfuric acid is used to convert protein nitrogen to ammonium sulfate at a boiling point elevated by the addition of potassium sulfate. A copper catalyst is used to enhance the reaction rate. An excess of sodium hydroxide is added to the cooled dig

34、est to liberate ammonia. The liberated ammonia is distilled, using a manual, semi-automatic or fully automatic steam distillation unit. In the case of manual or semi-automatic steam distillation, distillation of the ammonia into an excess of boric acid solution is followed by titration with hydrochl

35、oric acid solution to a colorimetric endpoint. Where a fully automatic system is employed, automatic titration of the ammonia is carried out simultaneously with the distillation and the endpoint of the titration can also be detected by means of a potentiometric pH system. The nitrogen content is cal

36、culated from the amount of ammonia produced. The crude protein content is obtained by multiplying the result by the conventional conversion factor of 6,25. NOTE In principle, sulfuric acid can also be used for the titration. 5 Reagents During the analysis, unless otherwise stated, use only reagents

37、of recognized analytical grade and distilled or demineralized water or water of equivalent purity. 5.1 Kjeldahl catalyst tablets, comprising 3,5 g of potassium sulfate and 0,4 g of copper(II) sulfate pentahydrate per tablet. These tablets are commercially available. Other types of tablet may be used

38、 provided that: a) they contain a quantity of potassium sulfate such that 7 g of potassium sulfate and 0,8 g of copper(II) sulfate pentahydrate can be dispensed using an integral number of whole tablets; and b) they do not contain salts of toxic metals such as selenium or mercury. 5.2 Sulfuric acid

39、(H2SO4), at least 98 % mass fraction, nitrogen-free (20 1,84 g/ml). 5.3 Hydrogen peroxide solution, containing approximately 30 g of H2O2per 100 ml. BS EN ISO 5983-2:2009ISO 5983-2:2009(E) ISO 2009 All rights reserved 35.4 Antifoaming agent. A silicone preparation is recommended, e.g. with a mass fr

40、action of 30 % aqueous emulsion. 5.5 Sodium hydroxide (NaOH) solution, approximately 40 % mass fraction, nitrogen-free ( 10 % mass fraction fat). It is possible to stop at this point and continue work the following day. If foaming is a problem, slowly add 3 ml to 5 ml of hydrogen peroxide (5.3). Swi

41、rl gently and let the reaction subside. Alternatively, a few drops of antifoaming agent (5.4) may be used. Attach the heat side shields to the tube rack. Place the exhaust manifold (6.4) tightly on the tubes and turn the water aspirator or scrubber (6.5) on completely. Place the rack of tubes in the

42、 digestion block pre-heated to 420 C (6.2). After 10 min, turn the water aspirator down until the acid fumes are just contained within the exhaust hood. A condensation zone should be maintained within the tube. After the bulk of the fumes of sulfur oxides have been produced during the initial stages

43、 of digestion, reduce the vacuum source to prevent loss of sulfuric acid. Digest for an additional 50 min. The total digestion time should be approximately 60 min. Turn the digestor off. Remove the rack of tubes with the exhaust still in place and put it in the stand to cool for 10 min to 20 min. Wh

44、en fuming has stopped, remove the manifold and shut off the aspirator. Remove the side shields. Allow the tubes to cool. Manual predilution of samples is recommended prior to distilling. Wearing gloves and eye protection, carefully add a few millilitres of water to each tube. If spattering occurs, t

45、his means that the BS EN ISO 5983-2:2009ISO 5983-2:2009(E) 6 ISO 2009 All rights reservedtubes are still too hot. Allow to cool for a few more minutes. Add water to each tube to a total volume of approximately 80 ml. If the sample solidifies, place the tube containing the diluted digest in the block

46、 digester and carefully warm with occasional swirling until salts dissolve, or distil for a further 30 s to 60 s. NOTE 1 Some instruments perform the addition of water automatically. The predilution before placing the tube in the instrument is only required if very solid cakes form. NOTE 2 Some dist

47、illation instruments start with the addition of steam before the addition of alkali, which leads to a dissolution of salt cakes and a less violent reaction during alkali addition. Crystallization during digestion can cause nitrogen losses. 9.3.2 Distillation Transfer the digestion tube (see 9.3.1) t

48、o the distillation unit (6.8). Where titration of the ammonia content of the distillate is performed manually, the procedure mentioned below applies. Where the distillation unit is fully automated to include titration of the ammonia content of the distillate, follow the manufacturers instructions fo

49、r operation of the distillation unit. Place a conical flask (6.9) containing 25 ml to 30 ml of the concentrated boric acid solution (5.7) under the outlet of the condenser in such a way that the delivery tube is below the surface of the excess boric acid solution. Adjust the distillation unit to dispense 50 ml of sodium hydroxide solution (5.5). Operate the distillation unit in accordance with the manufacturers instructions and distil off the ammonia liberated by the addition of the sodium hydroxide solution. Collect the distillate