DIN 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 (IS.pdf

1、October 2009DEUTSCHE NORM English price group 12No part of this standard may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 65.120!$Z-v“1551083www

2、.din.deDDIN EN ISO 5983-2Animal feeding stuffs Determination of nitrogen content and calculation of crude proteincontent Part 2: Block digestion and steam distillation method (ISO 5983-2:2009)English version of DIN EN ISO 5983-2:2009-10Futtermittel Bestimmung des Stickstoffgehaltes und Berechnung de

3、s Rohproteingehaltes Teil 2: Blockaufschluss- und Dampfdestillationsverfahren (ISO 5983-2:2009)Englische Fassung DIN EN ISO 5983-2:2009-10SupersedesDIN EN ISO 5983-2:2005-10www.beuth.deDocument comprises pages222 DIN EN ISO 5983-2:2009-10 National foreword This standard has been prepared by Technica

4、l Committee ISO/TC 34 “Food products” (Secretariat: AFNOR, France), Subcommittee SC 10 “Animal feeding stuffs” (Secretariat: NEN, Netherlands) in collaboration with Technical Committee CEN/TC 327 “Animal feeding stuffs Methods of sampling and analysis” (Secretariat: NEN, Netherlands). Based on the r

5、esults of parallel voting, ISO 5983-2:2009 was adopted as a European Standard. The responsible German body involved in its preparation was the Normenausschuss Lebensmittel und landwirtschaftliche Produkte (Food and Agricultural Products Standards Committee), Technical Committee NA 057-03-03 AA Futte

6、rmittel. The DIN Standards corresponding to the International Standards referred to in this document are as follows: ISO 385 DIN EN ISO 385 ISO 5275-1 DIN ISO 5725-1 ISO 5275-2 DIN ISO 5725-2 ISO 5983-1 DIN EN ISO 5983-1 ISO 6497 DIN EN ISO 6497 ISO 8655-2 DIN EN ISO 8655-2 ISO 8655-3 DIN EN ISO 865

7、5-3 ISO 8655-5 DIN EN ISO 8655-5 Amendments This standard differs from DIN EN ISO 5983-2:2005-10 as follows: a) Clause 11 “Precision” has been revised. b) A second interlaboratory test has been included in Annex A. c) The results of the second interlaboratory test are given in a new Table A.2. d) Fi

8、gure A.1 “Relationship between precision values and the mean crude protein content” has been added. e) Annex B has been modified to include the “Results of a proficiency test; comparison of the colorimetric and potentiometric endpoint determination of the titration”. f) The standard has been brought

9、 in line with the current rules of presentation. Previous editions DIN EN ISO 5983-2: 2005-10 3 National Annex NA (informative) Bibliography DIN EN ISO 385, Laboratory glassware Burettes DIN EN ISO 5983-1, Animal feeding stuffs Determination of nitrogen content and calculation of crude protein conte

10、nt Part 1: Kjeldahl method DIN EN ISO 6497, Animal feeding stuffs Sampling DIN EN ISO 8655-2, Piston-operated volumetric apparatus Part 2: Piston pipettes DIN EN ISO 8655-3, Piston-operated volumetric apparatus Part 3: Piston burettes DIN EN ISO 8655-5, Piston-operated volumetric apparatus Part 5: D

11、ispenser DIN ISO 5725-1, Accuracy (trueness and precision) of measurement methods and results Part 1: General principles and definitions DIN ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results Part 2: Basic method for the determination of repeatability and reproducibilit

12、y of a standard measurement method DIN EN ISO 5983-2:2009-10 4 This page is intentionally blank DIN EN ISO 5983-2:2009-10 EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 5983-2June 2009ICS 65.120 Supersedes EN ISO 5983-2:2005 English VersionAnimal feeding stuffs - Determination of nitrogen con

13、tent 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 vapeur (ISO 5983-2:2009)Futtermittel - Besti

14、mmung des Stickstoffgehaltes undBerechnung des Rohproteingehaltes - Teil 2:Blockaufschluss- und Dampfdestillationsverfahren 5983-2:2009)This European Standard was approved by CEN on 30 May 2009.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions f

15、or 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.This European Standard exists in three official

16、 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 the national standards bodies of Austria, Belgi

17、um, 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, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STA

18、NDARDIZATIONCOMIT 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 5983-2:2009: E(ISO2 Contents Page Foreword .3 1 Sco

19、pe4 2 Normative references4 3 Terms and definitions .5 4 Principle .5 5 Reagents 5 6 Apparatus.7 7 Sampling 7 8 Preparation of test sample .8 9 Procedure.8 9.1 General .8 9.2 Test portion8 9.3 Determination 8 9.4 Blank test .9 9.5 Recovery tests .10 10 Calculation and expression of results 10 10.1 C

20、alculation .10 10.2 Calculation of crude protein content.11 10.3 Expression of crude protein content results11 11 Precision 11 11.1 Interlaboratory tests11 11.2 Repeatability 12 11.3 Reproducibility 12 12 Test report12 Annex A (informative) Results of interlaboratory tests 13 Annex B (informative) R

21、esults of a profiency test; comparison of the colorimetric and potentiometric endpoint determination of the titration.17 Bibliography18 DIN EN ISO 5983-2:2009-10 EN 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

22、 collaboration with Technical Committee CEN/TC 327 “Animal feeding stuffs - 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

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

24、uch patent rights. This document supersedes EN ISO 5983-2:2005. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finl

25、and, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, 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

26、 ISO 5983-2:2009 without any modification. DIN EN ISO 5983-2:2009-10 EN ISO 5983-2:2009 (E) 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 r

27、esponsibility 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 to

28、 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 fr

29、action 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 determi

30、ne 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 referre

31、d 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) DIN EN ISO 5983-2:2009-10 EN

32、 ISO 5983-2:2009 (E) 43 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 percentage mass fracti

33、on 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 block digestion or equiv

34、alent 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 digest to liberate ammoni

35、a. 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 hydrochloric acid solution to

36、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 calculated from the amoun

37、t 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 of recognized analytic

38、al 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 provided that: a) the

39、y 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 (H2SO4), at least 98 %

40、 mass fraction, nitrogen-free (20 1,84 g/ml). 5.3 Hydrogen peroxide solution, containing approximately 30 g of H2O2per 100 ml. 5DIN EN ISO 5983-2:2009-10 EN ISO 5983-2:2009 (E) 5.4 Antifoaming agent. A silicone preparation is recommended, e.g. with a mass fraction of 30 % aqueous emulsion. 5.5 Sodiu

41、m 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). Swirl gently and let the reaction subside. Al

42、ternatively, 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 digestion block pre-heated to 420 C (6.2)

43、. 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 of digestion, reduce the vacuum source to

44、 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. When fuming has stopped, remove the manifold

45、 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, this means that the DIN EN ISO 5983-2:2009-

46、10 EN ISO 5983-2:2009 (E) 8tubes 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 digester and carefully warm with occasional swirling until sa

47、lts 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 distillation instruments start with the addition of steam before t

48、he 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) to the distillation unit (6.8). Where titration of the ammonia

49、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 for 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 dispens