ISO INTERNATIONAL STANDARD 6974-2 Second edition 2012-05-15 Natural gas Determination of composition and associated uncertainty by gas chromatography Part 2: Uncertainty calculations Gaz naturel - Détermination de la composition et de I'incertitude associée par chromatographie en phase gazeuse —Partie 2: Calculs d'incertitude Reference number ISO 6974-2:2012(E) LSO @ ISO 2012 IHS under itted without license from IHS Not for Resale ISO 6974-2:2012(E) COPYRIGHTPROTECTEDDOCUMENT ISO2012 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing 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 + 41 22 749 09 47 E-mail [email protected] Web www.iso.org Published in Switzerland @ ISO 2012 -All rights reserved No reproductic etworking permitted without license from IHS Not for Resale ISO 6974-2:2012(E) Contents Page Foreword .iv Introduction 1 Scope 2 Normative references 3 Terms and definitions 4 Symbols 4.1 Symbols.. 4.2 Subscripts 5 Calculationofuncertainty. 5.1 General considerations 5.2 Principles..... 5 5.3 Step 9 Calculation of uncertainty of mole fractions 5.4 Step 10 Calculation of the expanded uncertainty of mole fractions 11 Annex A (informative) Calculation of processed component uncertainties for the methane-by-difference approach.. 12 Annex B (normative) Uncertainties of relative response factors. .13 Annex C (informative) Alternative calculation of the uncertainty of the value of the unknown 14 Bibliography 16 ili se with I cense from IHS Not for Resale