ISO INTERNATIONAL STANDARD 16634-2 First edition 2016-05-15 Food products Determination of the total nitrogen content by combustion according to the Dumas principle and calculation of the crude protein content - Part 2: Cereals, pulses and milled cereal products Produits alimentaires - Détermination de la teneur en azote total par combustion selon le principe Dumas et calcul de la teneur en proteines brutes - Partie 2: Céréales, légumineuses et produits céréaliers de mouture Reference number IS0 16634-2:2016(E) ISO International Organization for Standardization @ IS0 2016 STANDARDIZATION C1 5956617 ed without license from IHS IS0 16634-2:2016(E) COPYRIGHT PROTECTEDDOCUMENT IS0 2016, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior 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 Ch. de Blandonnet 8 . CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 [email protected] www.iso.org Licensee-ZHEJIANG INST OF STANDARDIZAISQ 0d6 - All rights reserved HS und Not for Resale, 2016/7/20 08:02:04 networking permited without license from IHS IS0 16634-2:2016(E) Contents Page Foreword ..iv Introduction. ..V 1 Scope. ..1 2 Normative references ..1 3 Terms and definitions 4 Principle ..2 5 Reagents. ..2 6 Apparatus ...3 7 Sampling. ..3 8 Preparation of the test sample ..3 9 Procedure ..4 9.1 General. .4 9.2 Testportion .4 9.3 Control of oxygen supply ..4 9.4 Calibration .5 9.5 Determination .5 9.6 Detection and data processing ..5 10 Calculation and expression of results .6 10.1 Calculation .6 10.1.1Nitrogen content ..6 10.1.2 Crude protein content .6 10.2 Expression of results. ..6 11 Precision ..6 11.1 Interlaboratory tests ..6 11.2 Repeatability 11.3 Reproducibility 11.4 Critical difference. 7 11.4.1Comparison of two groups of measurements in the same laboratory 7 11.4.2 Comparison of two groups of measurements in two different laboratories ..8 11.5 Uncertainty .8 12 .8 Test report Annex A (informative) Flowchart for a basic Dumas apparatus ..9 Annex B (informative) Schematic diagrams of suitable types of Dumas apparatus ..10 Annex C (informative) Equipment calibration ..13 Annex D (informative) Results of interlaboratory tests ..15 Bibliography .22 iii icenSee=ZHEJIANG INST OF STANDARDIZATION C1 5956617 withoutlicense from IHS