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:

Link database: Hazardous Substances Data Bank: Seleno-(DL) cysteine
Speciation analysis and food security | EVISA's Agenda of Events
Material database: National Institute of Standards and Technology (NIST) - SRM 1632d - Trace Elements in Coal, (Bituminous)
A short report from the speciation workshop TraceSpec 2009 | EVISA's News
Material database: National Metrology Institute of Japan (NMIJ) - NMIJ CRM 7402-a Trace Elements, Arsenobetaine and Methylmercury in Cod Fish Tissue
9th International Conference on Mercury as a Global Pollutant (ICMGP) | EVISA's Agenda of Events
Link database: Metal Speciation Toxicokinetics Database: Selenium
Material database: IRMM - Institute for Reference Materials and Measurements - BCR-277R - Estuarine Sediment
Material database: Sigma-Aldrich - Matrix CRM - Soil, Sludge, Sediment: Trace Metals - Fresh Water Sediment 3
Material database: IRMM - Institute for Reference Materials and Measurements - BCR-713 - Wastewater effluent
Material database: IRMM - Institute for Reference Materials and Measurements - ERM-CE278 - Mussel tissue (mytilus edulis)
Instrument database: Austin AI, LLC - CP-1000 EDXRF system
Selenomethionine shows promising results as a protective agent against Esophageal Cancer | EVISA's News
Natural wetlands contribute significantly to elemental cycling by volatilization | EVISA's News
Instrument database: Agilent Technologies Inc. - 7500ce ICP-MS
Material database: The Food and Environment Research Agency (FAPAS) - Test Material T1861 (Energy drink)
Material database: IRMM - Institute for Reference Materials and Measurements - ERM-CD281 - Rye Grass
Material database: National Institute of Standards and Technology (NIST) - SRM 1946 Lake Superior Fish Tissue
Material database: RECIPE Chemicals + Instruments GmbH - ClinChek 8883 Control blood plasma, lyophilised, trace elements level I: LOT 1286
A new study finds: Inorganic mercury stays in the brain for years if not decades | EVISA's News