The provision and use of traceability statements for reference materials

Reference material certificates prepared in accordance with ISO 17034:2016 must include a statement of metrological traceability for each certified value. Users of these materials are required by accreditation bodies and other organisations to request the provision of such statements and to ensure that the stated traceability is fit for the intended use of the material. However, ISO 17034:2016 says nothing about the format to be adopted for such statements. Several possibilities are described in guidance documents published by the ISO Committee for Reference Materials (ISO/REMCO) but these sometimes lack clarity and consistency. One reason for this is the absence of a clear consensus on the appropriate content of such statements. The UK Reference Materials Working Group has addressed this situation with an extensive discussion of the issues. This paper summarises the Group's conclusions on the purpose, drafting and interpretation of traceability statements for certified values of reference materials, including matrix materials, pure calibrants and calibration solutions. It will be of interest to producers and users of reference materials and also accreditation bodies which accredit facilities to the conformity assessment standards ISO 17034:2016 and ISO/IEC 17025:2017. The document includes a brief overview of four aspects of traceability which impact the preparation of traceability statements: the basis of metrological traceability; the reason for adopting traceable measurements; the type of information on traceable values required by users of reference materials; and how to present information on traceability in the form of a traceability statement.