4.  Reference materials

4.1 Mutual recognition agreement

Once confidential, reference materials (RMs), especially when certified, are playing an increasingly significant role in modern analytical sciences. In fact, ISO has set up a special Reference Material Committee (REMCO). It has defined two types of RM:

• simple reference materials, the homogeneity and stability of one or more properties of which have been sufficiently established to make them suitable for the validation of a defined measurement procedure; this definition is fully applicable to the surplus of samples which may be available from a proficiency testing scheme realization (§