Establishment of SI-traceable reference ranges for the content of various elements in the IMEP-9 water sample

The International Measurement Evaluation Programme (IMEP) attempts to shed light on the current state of the practice in chemical measurements. The ma in tool, which assists this attempt and also differentiates IMEP from simil ar projects, is the establishment of SI-traceable reference ranges (where p ossible) for the elements offered for measurement to the participants for e very IMEP round. The Institute for Reference Materials and Measurements (IR MM), as the founder and co-ordinator of IMEP has the responsibility of esta blishing the SI-traceable reference ranges. This is a large task that requi res knowledge, skill and resources. IRMM collaborates with a network of ref erence laboratories in order to achieve the establishment of SI-traceable r eference ranges in a transparent and reliable way. The IMEP reference labor atories must have demonstrated experience and have a proven and successful record in the use of primary methods of measurements (mainly isotope diluti on mass spectrometry) and the application of uncertainty evaluation accordi ng to ISO/BIPM guidelines. In IMEP-9 'trace elements in water", results fro m 7 reference laboratories (including IRMM) were combined by IRMM to establ ish SI-traceable ranges for the 15 elements, which were then offered for me asurement to the 200 participants worldwide. This paper does not discuss th e individual contribution of the reference laboratories (this could be the subject of individual papers) but describes the procedures and criteria use d in order to establish the reference ranges for the IMEP-9 samples by comb ining the individual contributions. All results submitted to IRMM are inclu ded, so as to make this publication as realistic as possible.