ISO INTERNATIONAL STANDARD 10980 First edition 1995-08-15 Validation of the strength of reference solutions used for measuring concentrations Vérification du titre des solutions de référence utilisées pour la mesure des concentrations ISO Reference number ISO 10980:1995(E) Coovriaht International Oraanization for Standardization IS010980:1995(E) Foreword Iso (the International Organization for Standardization) is a worldwide of preparing International Standards is normally carried out through IsO which a technical committee has been established has the right to be represented on that committee.International organizations,governmental and non-governmental, in liaison with IsO, also take part in the work. Iso collaborates closely with the International Electrotechnical Commission (lEC)onall mattersof electrotechnicalstandardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. ISO/TC85, Nuclear energy. Subcommittee Sc 5,Nuclearfuel technology. AnnexesA, B and C form an integral part of this International Standard. Annexes D, E, F, G, H and J are for information only. ISO 1995 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced microfilm, without permission in writing from the publisher. International Organization for Standardization CasePostale56·CH-1211Geneve20·Switzerland Printed in Switzerland i INTERNATIONALSTANDARDISO ISO10980:1995(E) Validation of the strength of reference solutions used for measuring concentrations Scope The reference solutions used for the standardization of analytical methods are the means through which the final result of the analysis is traceable to the basic units and to their standards. The strength of these solutions should therefore be traceable to these same units with a relative accuracy of ± 0,1 % or better. This International Standard specifies procedures for preparing reference solutions, as well as a set of procedures for ensuring the quality of theirpreparation and the degree of accuracy of the solution strength. It is intended to be a working document for analytical chemists.The underlying statistical theory is therefore not presented in full details or rigorously, in order to simplify application. Sufficient details are included in annex H, in order to implement the procedure step by step in a laboratory en- vironment. 2Principle Uranium,plutoniumand potassium dichromate reference solutions are prepared independently These reference solutions are prepared exclusively from certified reference materials or from materials which have been analysed by at least two independent methods. Exactly weighed quantities of these materials are dissolved quantitatively and the solutions thus obtained arethemselves weighed exactly. The solution strengths are calculated from weighing data and from the known composition of the source materials. The accuracyof theirpreparation is checkedbycomparingthese solutionsbetweenthemselveswiththehelp of analytical methods so that the relative difference △ between Ac, the strength calculated for these solutions, and Am, the mean of replicate measurements, does not exceed 0,1 %. Two categories of reference solutions can be distinguished according to the quality of the materials used in their preparation: -primaryreference solutions; - secondary reference solutions. 3 Primary reference solutions Primary reference solutions are prepared from reference materials which are distributed by approved organizations certifying their composition with a relative uncertainty of o,o5 % or better, corresponding to the confidence interval for a probability level of 95 %.