(1997; 248 pages) [French]
2. Evaluation of reference substances
Evaluation of the suitability of a material proposed for use as a reference substance requires careful testing. It is necessary to consider all data obtained by examining the material, employing a wide variety of analytical methods. When taken as a whole they give confidence that the material is suitable for the intended use. Depending on the intended use of the substance, testing can be more or less searching and involve a number of independent laboratories.
In the case of reference substances that are intended for use in the identification tests or in the determination of purity, the examination may be carried out without a unified programme, all analytical data obtained in different laboratories being then considered. If compatible results are obtained in all the collaborating laboratories, a positive decision concerning the suitability of the material can be arrived at. The procedure may be simplified in the case of the evaluation of replacement batches of an existing reference substance.
When it is necessary to assign quantitative values to a reference substance, a collaborative study, following a carefully designed protocol and employing at least three cooperating laboratories, should be undertaken.