Eurachem’s 25th anniversary: two members’ perspective

Abstract

Eurachem was founded 25 years ago. Its prime aim, as wasset out in the Memorandum of Understanding (MoU)signed by its members, was to help establish a system ofinternational traceability for chemical analysis. At thattime, there was little international activity in this topic or inthe broader field that could be classified as Metrology inChemistry (MiC); in fact, the concept ‘‘Metrology inChemistry’’ was hardly in use. The ‘‘Guide to the Expres-sion of Uncertainty in Measurement’’ (GUM) [1] had not yetbeen published, but there had been a lot of activities on theevaluation of uncertainty in the higher echelons of physicalmeasurements following the publication of recommenda-tions of the International Bureau of Weights and Measures(BIPM) working party on ‘‘Expression of MeasurementUncertainties’’ in 1980. This way of evaluating andreporting uncertainty had also percolated to other areas ofphysical measurement but had attracted little or no attentionfrom analytical chemists. As a matter of fact, the Interna-tional Committee for Weights and Measures (CIPM) onlystarted to take interest in chemical measurement in the lateeighties.The GUM was published in 1993 based on these BIPMrecommendations, and it is such an important landmark inthe development of metrology that it is worth repeating itsbasic principles and the changes these engendered. Previ-ously, most of the discussion and reporting of accuracy hadbeen based on the concept of a ‘‘true value’’ and randomand systematic errors. Since the true value is unknown andunknowable, and systematic errors are difficult if notimpossible to evaluate, accuracy statements were mainlybased on measurement repeatability or in some casesreproducibility. GUM changed all that, as is stated in theintroduction to Annex D, ‘‘the concept of uncertaintyadopted in this guide is based on the measurement resultand its evaluated uncertainty rather than the unknowablequantities ‘‘true’’ value and error.’’GUM found fairly rapid adoption for physical mea-surements. However, it had received very little attention inchemical measurements before the publication in 1995 ofthe guide ‘‘Quantifying uncertainty in analytical measure-ment’’ by Eurachem and CITAC (Cooperation onInternational Traceability in Analytical Chemistry), afterwhich, together with pressure from the accreditation bod-ies, uncertainty evaluation became common practice as isexemplified by its use in a large number of articles in thisjournal.It is strange that uncertainty evaluation was the first stepin applying MiC principles, rather than establishment oftraceability of measurement results, particularly since it isthe latter that was a primary aim of Eurachem. A workshopon ‘‘Traceability and Comparability’’ was held at theCentral Bureau for Nuclear Measurements (CBNM, laterthe Institute for Reference Materials and Measurements(IRMM)) in November 1992, but it was a number of years,with much discussion and many papers [2] before the firstreal concepts started to be developed on how to establishtraceability, and the Eurachem/CITAC Guide ‘‘Traceabilityin chemical measurement’’ was not published until 2003.The solution turned out to be very similar to that forphysical measurements, i.e. establishment of traceabilityfor all of the measured values of quantities that are in the