ABSTRACT
Speciation analysis is necessary to identify the Selenium speciation in the tissues to see which proportion of Se is biological active. In biological samples, Se may occur additionally in a number of biological molecules, such as the two amino acids selenocysteine (SeCys) or selenomethione (SeMet), which can be incorporated into proteins. Speciation methods involving proteolytic digestions, which are used to determine SeCys and SeMet, need to be employed to identify whether the Se status as essential Se is guaranteed. Se in the form of selenate or selenite is often used in fertilizers, and it has been shown that the uptake of Se into the upper parts of the plants is often inefficient. In plants, Se speciation would involve the detection of Se biotransformations into selenide, which is then incorporated into glutathione or phytochelatins. The mass balance often identifies losses of Se due to the formation stable elemental Se in the soil.
