selenium

Selenium is a chemical element with atomic number 34, with the chemical symbol Se. Selenium occurs only rarely in the free state in nature. It is a nonmetal that is chemically related to sulfur and tellurium. It is toxic in large amounts, but trace amounts of it, forming the active center of certain enzymes such as glutathione peroxidase(GSH-Px), are necessary for the function of all cells in (probably) all animals. Selenium requirements in plants differ by species, with some plants apparently requiring none.

Isolated selenium occurs in several different forms, but the most stable of these is a dense purplish-gray semimetal (semiconductor) form that is structurally a trigonal polymer chain. It conducts electricity better in the light than in the dark, and is used in photocells (see allotropic section below). Selenium also exists in many nonconductive forms: a black glass-like substance, as well as several red crystalline forms built of eight-membered ring molecules, like its lighter cousin sulfur.

Selenium is found in economic quantities partially replacing sulfur in sulfide ores such as pyrite. Minerals that are selenide or selenate compounds are also known, but all are rare.



The term "selenium" was found in the following pages:

Directory of scientists: Juris Meija
Material database: Sigma-Aldrich - Matrix CRM - Soil, Sludge, Sediment: Trace Metals - Fly Ash 3
Material database: RECIPE Chemicals + Instruments GmbH - ClinChek 8884 Control blood plasma, lyophilised, trace elements level II: LOT 129
Link database: Hazardous Substances Data Bank: Selenium oxychloride
Material database: IRMM - Institute for Reference Materials and Measurements - BCR-185R - Bovine Liver
Material database: JRC - Joint Research Centre - ERM-CE101 TROUT MUSCLE (trace elements)
Adisseo obtains FDA approval on pure organic selenium feed additive | EVISA's News
Link database: ChEBI: L-selenohomocysteine
EU approves new selenium compound for use as a nutritional supplement in animals | EVISA's News
High Accumulation of Selenium in Wheat Grains | EVISA's News
Instrument database: Analytik Jena AG - HydrEA
Link database: Hazardous Substances Data Bank: Seleno-(DL) cysteine
Material database: Sigma-Aldrich - Matrix CRM - Soil, Sludge, Sediment: Trace Metals - Fresh Water Sediment 2
Certified Reference Materials for Chemical Speciation Analysis | EVISA's News
Material database: National Research Council of Canada (NRC - CNRC) - DOLT-4: Dogfish liver certified reference material for trace metals
Instrument database: PS Analytical - 10.055 Millennium Excalibur
Material database: RECIPE Chemicals + Instruments GmbH - ClinChek 8881 Blood Serum Control lyophilised, trace elements level II
Researchers discover how selenium is incorporated into proteins | EVISA's News
Accurate determination of arsenic and its species by internal standardization for quantification by ICP-MS | EVISA's News
Material database: National Research Council of Canada (NRC - CNRC) - LUTS-1: non defatted lobster hepatopancreas