Legal and Statutory Requirements

In general, the question you should always ask is, What will the results of the analysis be used for . If you are sampling for compliance with a contractual requirement, i.e. the sample must contain a minimum/maximum amount of the analyte, then it is important to know how this is interpreted. At the time of writing, the Codex Alimentarius Commission recommended the following limits for food-grade salt [12]  

One needs to know if this means, Individual items in a lot may not exceed 

Each of these interpretations requires a different approach. Note that blending material from a number of items prior to analysis (or averaging results obtained from a number of different items) may mean that hot spots of the analyte in the sample are overlooked. This will be important if the purpose of the analysis is to study contamination which may affect only certain items (see Section 3.2.2). 

There may also be cases where the maximum amount of analyte permitted is fixed by law, i.e. statutory limits. For these, there may be laid down standard procedures for sampling. The Codex maximum residue limit for the pesticide cypermethrin is 2 mg kg-1 (at the time of writing) in both citrus fruits and peaches [13]. When preparing the sample for analysis you need to know that in the case of the citrus fruit you take the whole fruit - skin, pith, pips, flesh and juice - whereas in the case of peaches it is the fruit after removal of stems and stones, but the residue is calculated and expressed in terms of the whole commodity (including the stone) without stems [14]. In some instances, it may be necessary to take a certain number of samples and that these must be taken in the presence of a witness. 

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To understand the importance of sampling plans and appreciate the legal and statutory requirements. 

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