Choice of the CRM

The criteria for the choice of the CRM are not different from the criteria to select the material for the preparation of a laboratory reference material for method development, statistical control charts etc. The difference lies in the availability of adequate CRMs from reliable suppliers and the level of compromise which the analyst must make between an ideal situation and the reality of what is on offer. Massart and co-workers have proposed a principle component analysis to help select the best adapted CRMs available on the market to verify AAS analysis of foodstuffs [10], Their approach took into account the analytes as well as the matrix composition. Besides the fact that they highlighted a lack of sorts of CRM, in particular those having a fatty matrix, they demonstrated that such a statistical approach can help in the most appropriate selection of materials. Boenke also proposed a systematic approach for the choice of materials to be certified for mycotoxins [11] and which could be followed by potential users. The selection of the CRM by the analyst should include a certain number of parameters this can cover the following properties to fulfil the intended purpose level of concentration of the analytes  

Many of the above properties will be discussed in the chapter dealing with the production of CRMs. The performance criteria required from the CRMs and the way to exploit them are discussed here. 

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