Characterization of reference materials: proposal for a simplification of the options listed in ISO Guide 34

ISO Guide 34 and 35 list 4 approaches for the characterization of reference materials. We argue that an approach using "one method of demonstrable accuracy, performed by a network of competent laboratories" will provide method-specific values. Furthermore, as it is impossible to objectively decide whether a method is a reference method or not, the approach using "two or more independent reference methods in one or several laboratories" should be combined with the approach "two or more methods of demonstrable accuracy, performed by a network of competent laboratories." We therefore propose to replace the four characterization approaches by three in the ongoing revision of ISO Guide 35.