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.