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News article19 March 2019

New ISO Guide 35: what needs to be known when producing CRMs

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Reference Materials
© EC, 2019

Certified reference materials (CRMs) are important quality assurance tools for precise measurements. Scientists from the JRC and the National Metrology Institute of South Africa elaborated on the principles for the characterisation and value assignment of reference materials according to the new ISO guide 35, aiming to facilitate the interpretation of the new guide.

The 'European Round Table of Industrialists' identified non-tariff barriers as one of the main factors hindering the free movement of goods.

The '1992 programme', resulting in the Maastricht Treaty and the EU internal market removed the legal basis for many of these barriers. However, an efficient internal market requires in many cases that measurement results are accepted throughout the Union.

Several factors contribute to the reliability of such a common measurement system, amongst others: accreditation, proficiency testing and Certified Reference Materials (CRMs). The latter allows laboratories to demonstrate to themselves and their customers that their results are reliable enough to base decisions on them.

As the JRC has a dedicated activity on reference material production - being a CRM producer to support especially EU Member States in the implementation of EU legislation - it is accredited itself according to ISO 17034 (general requirements for the competence of reference material producers) and follows closely the new ISO Guide 35.

While the standard (ISO 17034) described the requirements in a general way, ISO Guide 35 gives detailed explanations how to implement this standard. The general requirements laid out in ISO 17034 include a characterisation strategy.

As characterisation approaches are important for reference materials production, scientists from the JRC and the National Metrology Institute of South Africa provided a more easy to read summary to the new ISO Guide 35 chapter on characterisation.

In their summary report, they explain in more detail in the new ISO Guide 35:2017, with particular attention being paid to changes from the 2006 edition. Important changes include a clear distinction between using a single method in a single-laboratory when the method can be validated with a Certified Reference Material (CRM) of the same kind as the candidate reference material compared to a situation when a similar CRM is not available.

For the approach, where more than one method is used in one or more laboratories, the concept of the importance of the number of independent data sets is explained in more detail. A lot more technical detail is also provided for the use of an inter-laboratory comparison for the certification study.

This summary report aims to support the rapid implementation of ISO 17034 by reference material producers worldwide. In this way harmonised production processes for CRMs are ensured.

Read more in T.P.J. Linsinger, A. Botha, "Principles for the characterisation and the value assignment of the candidate reference material in the new ISO Guide 35:2017", Accred. Qual. Assur., in press (2019), https://doi.org/10.1007/s00769-018-1364-2

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Principles for the characterisation and the value assignment of the candidate reference material in the new ISO Guide 35:2017

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Publication date
19 March 2019