ISO INTERNATIONAL STANDARD 18643 First edition 2016-04-01 Fertilizers and soil conditioners Determination of biuret content of urea-based fertilizers HPLC method Engrais et amendements - Détermination de la teneur en biuret des engrais a base d'urée - Méthode HPLC Reference number ISO 18643:2016(E) ISO International Organization for Standardization @ IS0 2016 =ZHEJIANG INST OF STANDARDIZATION C1 5956617 vided by IHS under ted without license from IHS IS0 18643:2016(E) COPYRIGHTPROTECTEDDOCUMENT 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 written permission. Permission can be requested from either ISO at the address below or ISO's member body in the country of the requester. ISOcopyrightoffice 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 Internatinair PrganizationforStandardization nsee-ZHEJIANG INSTOF STANDARDIZAoSQ6- All rights reserved Not for Resale, 2016/6/2 08:56:0 etworking permitted without license from IHS IS0 18643:2016(E) Contents Page Foreword ..iv Introduction. ..V 1 Scope. ..1 2 Normative references 3 Principle 4 Reagents. .1 5 Apparatus. ..1 6 Procedure .2 6.1 Preparation of test sample .2 6.2 Preparation of test solution .2 6.3 Preparation of biuret working standard solutions 2 6.4 HPLC conditions. .2 6.5 Preparation of standard curve. .3 6.6 Determination of the biuret content in the test solution .3 6.7 Calculation and expression of the results 3 6.8 Precision. .3 6.8.1 Ring test 3 6.8.2 Repeatability, r ..4 6.8.3 Reproducibility, R .4 7 Test report Annex A (informative) Report of international laboratories ring test ..5 Annex B (informative) Alternative method for determination of biuret in fertilizers ..11 Bibilography ..12 iii e=ZHEJIANG INST OF STANDARDIZATION C15956617 vided by IHS under I ithout license from IHS