Selection of the test material

All participants should receive identical test samples in order to make results as obtained by the laboratories comparable. The material prepared for the exercise should meet requirements set by the objective of the study. Basic quality requirements for reference materials used in interlaboratory studies are described in chapter 4 of this book and the reader should refer to this chapter for matters related to the choice and representativeness of the test materials. The material prepared should be homogeneous its stability should be guaranteed at least over the duration of the study. 

The measures to be taken to guarantee the homogeneity and the stability of the test samples may affect the representativeness of the material and obligation to compromise. 

When the matrix has been chosen with regards to the feasibility as discussed above and when the parameters to be measured are clearly defined, the collection and the preparation of the test material may start. All requirements of quality, except the certification of the content of certain substances, are valid for all type of reference materials used in interlaboratory studies. These detailed requirements, the preparation and control procedures should be available from the organiser in a production report. They are discussed in more detail in the chapter 4 dealing with (C)RM. 

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