Speciation is a promising and essential tool in the evaluation of the contamination of metals in food and environmental samples. In this context, information about the species of these elements is important considering that toxic effects are directly related to their chemical forms. The enormous progress in combining separation and detection techniques has enabled the effective chemical speciation. However, a possible source of error in studies of speciation occurs during sample preparation. Appropriate treatment of samples is necessary in order to ensure that interconversion between the species does not occur during the experimental procedure prior to the final analysis. In this review, methods of sample preparation for the determination of arsenic and selenium in food and environmental samples are discussed. We decided to focus on these elements since they account for around 50% of all speciation studies. Procedures including conventional extraction, microwave-assisted extraction and sonolysis are discussed as simple ways to ensure species selectivity. The main purpose of this review is to provide an update on the recent literature concerning the strategies for arsenic and selenium speciation and to critically discuss their advantages and weaknesses compared with the commonly accepted approach of combining non-chromatographic and spectroscopic techniques. The problems focused on involve sampling, sample preparation and storage, as well as changes in ‘species information’ that occur during the use of various separation technologies. These difficulties are described along with recent developments aimed at overcoming these potential issues.
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