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Selenocysteine is an analogue of the more common cysteine with selenium in place of the sulfur. Selenocysteine is present in several enzymes (for example glutathione peroxidases , tetraiodothyronine 5′ deiodinases , thioredoxin reductases , formate dehydrogenases , glycine reductases , selenophosphate synthetase 2 , methionine- R -sulfoxide ...
Selenium is found in metal sulfide ores, where it substitutes for sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores. Minerals that are pure selenide or selenate compounds are rare. The chief commercial uses for selenium today are glassmaking and pigments. Selenium is a semiconductor and is used in photocells.
A blank solution is a solution containing little to no analyte of interest, [1] usually used to calibrate instruments such as a colorimeter. According to the EPA, the "primary purpose of blanks is to trace sources of artificially introduced contamination." [2] Different types of blanks are used to identify the source of contamination in the ...
After selenium is in the sediment, other chemical and microbial reduction may occur, causing insoluble organic, mineral, elemental, or adsorbed selenium. Some organic forms may be released into the atmosphere from volatilization by chemical or microbial activity in the water and sediment or by direct release from plants.
Selenium forms two oxides: selenium dioxide (SeO 2) and selenium trioxide (SeO 3). Selenium dioxide is formed by the reaction of elemental selenium with oxygen: [5] + It is a polymeric solid that forms monomeric SeO 2 molecules in the gas phase. It dissolves in water to form selenous acid, H 2 SeO 3.
[1] [2] [3] Selenium belongs with oxygen and sulfur to the group 16 elements or chalcogens, and similarities in chemistry are to be expected. Organoselenium compounds are found at trace levels in ambient waters, soils and sediments. [4] Selenium can exist with oxidation state −2, +2, +4, +6. Se(II) is the dominant form in organoselenium ...
Diagram which depicts the basics of flow injection analysis. A sample is injected into a flowing carrier solution stream that is forced by a peristaltic pump. The injection of the sample is done under controlled dispersion in known volumes. The carrier solution and sample then meet at mixing points with reagents and react.
Selenium deficiency occurs when an organism lacks the required levels of selenium, a critical nutrient in many species.Deficiency, although relatively rare in healthy well-nourished individuals, [1] can have significant negative results, [2] affecting the health of the heart and the nervous system; contributing to depression, anxiety, and dementia; and interfering with reproduction and gestation.