Reference materials: terminology and use. Can't one see the forest for the trees?

The use of reference materials (RMs) and the regular participation in proficiency testing (PT) schemes have become fundamental pillars of assuring and controlling the quality of analytical data in terms of precision and accuracy, thus proving the competence of analytical laboratories. In recent times, many terms describing non-certified reference materials (non-certified RMs) have emerged, often the result of confusing use with characteristics. Depending on the use of a material, a certain number of characteristics (e.g., homogeneity and assigned value) must be demonstrated. This article reviews the main types of application of RMs and describes the main material characteristics needed to fulfill the corresponding purposes. Based on this, it summarizes minimum requirements for certain uses. (C) 2004 Published by Elsevier B.V.