Chemical contaminants are compounds that are likely to have harmful effects on human health and/or other living organisms. Therefore, we need to be able to analyze them in various samples (foods, pharmaceuticals or environmental).

However, contaminant analysis is delicate. Indeed, the compounds in which we are interested are usually present in the sample at trace levels (or ultra-trace levels – see figure); that is why sensitive and selective analytical methods are necessary. Besides, there are many sources of error that may bias the analytical result.

In this sheet, the analytical approach to carrying out such analyses, as well as the main pitfalls that could falsify the analytical results, will be detailed.

Figure: compound content (in mass fraction) and usual expression of the content. 1 ppt = 10 exp -12, 1 ppb = 10 exp -9, 1 ppm = 10 exp -6, 0.1% = 10 exp -3. Ultra trace compounds = 10 exp -15 to 10 exp -5. Limitations of analytical methods for levels below 1 ppt (10 exp -12).
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