Traceability provides the terminology, concepts and strategy for ensuring that analytical chemical measurements are comparable. At present, the reference points are often internationally agreed methods; they can also be reference materials. Ideally there should be a single reference point, which in the case of chemistry is the SI Unit the mole, but much work will be required to achieve such a situation. Traceability does not imply high accuracy and levels of certainty consistent with fitness for purpose criteria is the goal. This paper discusses the relevance of the concept of traceability and reviews developments leading to a conceptual model for analytical chemistry. It also reports some recent work and considers future needs.

The selection of an appropriate isotope dilution mass spectrometry technique for the practical application of this potentially primary method of analysis is highly important. The NARL approach for the application of the exact matching double isotope dilution mass spectrometry technique developed by Henrion is presented. NARL's approach utilises exact matching to minimise the effect of measurement biases within the method but also includes the thorough examination of all other biasing factors. The approach has been successfully tested in international CCQM intercomparisons with other national metrology institutes.

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Titrimetry has wide-ranging applications for amount-of-substance measurements and can be used for both metrological and working-level measurements. This paper is a review of the potential of titrimetry as a primary method. Many parts of a traceability system are in place but these are not formally recognized at either a national or international level. Further work is required to assess existing expertise and to establish internationally recognized primary reference materials (standards) and measurement procedures.

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