EAL interlaboratory comparison Wa1 – Testing of potable water

 The accreditation of laboratories has emphasized the use of interlaboratory comparisons as a tool to monitor the comparability and accuracy of results laboratories produce. An interlaboratory comparison for water laboratories was organized among European Cooperation for Accreditation (EA) member countries; 30 laboratories, 7 of which were not accredited, from 14 European countries participated in this intercomparison. All the laboratories were chosen by the appropriate national accreditation bodies, with the instruction to select as participants those laboratories which act as national reference laboratories in this field. About 90% of the data collected was considered satisfactory after statistical treatment. Non-accredited laboratories performed as well as accredited laboratories. The laboratories were asked to take corrective action and report the corrections to the accreditation bodies. A great variation in the reported uncertainties of the results was observed. There seems to be a need to organize EA interlaboratory comparisons for national reference laboratories analysing water. It is obvious that even reference laboratories need training in how to estimate the uncertainty of results. Received: 22 July 1998 · Accepted: 21 September 1998