ISO INTERNATIONAL STANDARD 20483 Second edition 2013-12-01 Cereals and pulses - Determination of the nitrogen content and calculation of the crude protein content - Kjeldahl method Céréales etlégumineuses-1 Deétermination de la teneur en azote et calcul de la teneur en protéines brutes - Méthode de Kjeldahl Reference number IS0 20483:2013(E) LSO IS02013 HS under ed without license from IHS Not for Resale IS0 20483:2013(E) COPYRIGHTPROTECTEDDOCUMENT @ IS0 2013 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form written permission. Permission can be requested from either ISO at the address below or ISO's member body in the country of the requester. ISO copyright office Case postale 56:CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax +4122 749 09 47 E-mail [email protected] Web www.iso.org Published in Switzerland @ IS0 2013 - All rights reserved No reproductic networking permited without license from IHS Not for Resale IS0 20483:2013(E) Contents Page Foreword ..iv 1 Scope .1 2 Normative references .1 3 Terms and definitions 4 Principle 5 Reagents. ..2 6 Apparatus. ..3 7 Sampling. ..3 8 Preparation of test sample ..3 9 Determination of the moisture content ..4 10 Procedure ..4 10.1 General .4 10.2 Testportion 4 10.3 Determination ..4 10.4 Blanktest .5 10.5 Test with reference material (check test) .5 11 Expression of results .5 11.1 Nitrogen content. .5 11.2 Crude protein content .6 12 Precision .6 12.1 Interlaboratory test .6 12.2 Repeatability 6 12.3 Reproducibility ..6 12.4 Critical difference. .6 13 Test report .7 Annex A (informative) Results of interlaboratory tests. .8 Annex B (informative) Critical difference and practical application of the repeatability and reproducibility limits to differentprotein contents. ..10 Annex C (informative) Factors for converting nitrogen content to protein content ..12 Bibliography .13 iii se with IS ithout license from IHS Not for Resale