Determination of chemical species of elements (speciation) in the environment

This article presents the analytical techniques available for speciation analysis of trace elements in environmental samples. It is now recognized that measuring the total concentration of an element does not provide reliable information on its environmental impact and toxicity. This information can only be obtained by speciation analysis, the principle of which is to identify and measure the different chemical forms of elements. This approach requires strict sampling, preservation and sample preparation protocols that do not alter the distribution of chemical forms. These protocols are detailed in this dossier, together with the available instrumental techniques. In most cases, these are based on the on-line combination of a separative method (chromatographic methods) and detection by atomic spectrometry (ICP-MS, AFS). This article also presents some applications of methods enabling speciation analysis directly on solids. Their main advantage is that they do not require chemical extraction, thereby reducing the risk of species degradation. However, their lack of sensitivity means that accurate information cannot always be obtained. Finally, the main tools for validation (use of certified reference materials) and for improving the reliability of results (isotopic dilution) are described in detail.