3. Choose validation materials and set their reference values

At least three materials with known contents are required for testing. According to NF EN ISO/CEI 17025 – General requirements for the competence of testing and calibration laboratories, there are four types, depending on the method to be validated:

• methods for which MRCs are available;

• methods for which a reference method exists ;

• methods for which proficiency tests are organized and MREs are available;

• other methods for which none of the above solutions is available.

With the example given, it would be possible to use proposition 2, since an official method exists. Nicotinamide is commercially available in known purity (95%). To obtain known concentration levels, the dosed addition method was preferred....