BAÜ Fen Bil

The essential nature of selenium as well as its toxicity depend on the concentration and the chemical forms in which this element is present in environmental and biological samples. Dissolved inorganic selenium can be found in natural waters and soils as selenides, selenite and selenate. Organoselenium compounds that may be present in air, soils and plants are volatile methylselenides, trimethylselenonium ion and several selenoamino acids. This review article intends to show some general ideas and important procedures used for speciation analysis of selenium in particular matrices such as water, air, soils and plants. Introduction Selenium is the one of the most interesting elements from the point of view of its clinical and environmental effects. This element has been recognised as an essential nutrient for humans based on its presence in the enzyme glutathione peroxidase, which affords cells protection against oxidative damage. It is also important to mention other roles of selenium such as anticarcinogenic activity and preventing heavy metal toxic effects [1,2]. However, the nutritionally required concentration range of selenium is very narrow. A deficiency occurs when its intake is below 50 μg per day and daily doses up to 200 μg are considered as optimum [3]. Chronic selenium dietary deficiency has been associated with various degeneration diseases. Apart from natural sources (mainly metal-sulfur minerals) selenium compounds are widely spread throughout the environment from the combustion of fossil fuels, and uses in the glass and electronic industries as well