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:

Material database: RECIPE Chemicals + Instruments GmbH - ClinChek 8881 Blood Serum Control lyophilised, trace elements level II: LOT 347
Material database: IRMM - Institute for Reference Materials and Measurements - ERM-BB422 - Fish muscle
Material database: Sigma-Aldrich - Matrix CRM - Soil, Sludge, Sediment: Trace Metals - Chalky Loam 1
Trimethylselenonium is not the major metabolite for human cancer patients excreting high doses of selenium | EVISA's News
Researchers discover how selenium is incorporated into proteins | EVISA's News
Determination of tungsten species in natural waters by HPLC-ICP-MS | EVISA's News
The human liver: not always doing the job right? | EVISA's News
Material database: Sigma-Aldrich - Matrix CRM - Soil, Sludge, Sediment: Trace Metals - Fresh Water Sediment 3
Link database: Selenium and Soils in the Western United States
Instrument database: Aurora Instruments Ltd. - LUMINA 3300 Atomic Fluorescence Spectrometer
Prenatal Mercury Exposure Cancels Out Cognitive Benefits of Exercise | EVISA's News
Material database: Food Analysis Performance Assessment Scheme (FAPAS) - Test Material T07123 (Infant Formula, Cereal)
The role of electrochemical techniques for speciation analysis | EVISA's News
Speciation Analysis - Striving for Quality | EVISA's News
Material database: International Atomic Energy Agency (IAEA) - IAEA-155 Trace Elements in Whey Powder
Material database: IRMM - Institute for Reference Materials and Measurements - BCR-664
Material database: JRC - Joint Research Centre - ERM-CD281 - Rye Grass
Determination of arsenic species in water by means of capillary electrophoresis coupled to electrospray mass spectrometry | EVISA's News
Instrument database: Analytik Jena GmbH - contrAA 800 F - HRCS- Atomic absorption spectrometer for flame and hydride techniques
Material database: Food Analysis Performance Assessment Scheme (FAPAS) - Test Material T1094 (Dairy Ration)