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{{About||nitrates in medicine|Nitrovasodilator|the ion with chemical formula {{chem|NO|2|−}}|nitrite}}{{Chembox| ImageFile1 = Nitrate-3D-balls.png| ImageAlt1 = Ball-and-stick model of the nitrate ion| ImageFileR1 = | ImageAltR1 = Space-filling model of the nitrate ion| SystematicName = Nitrate| IUPACName =| OtherNames =| Section1 = {{Chembox Identifiers| CASNo = 14797-55-8| PubChem = 943| SMILES = [N+](=O)([O-])[O-] | ChemSpiderID = 918| InChI = 1/NO3/c2-1(3)4/q-1| InChIKey = NHNBFGGVMKEFGY-UHFFFAOYAI| StdInChI = 1S/NO3/c2-1(3)4/q-1| StdInChIKey = NHNBFGGVMKEFGY-UHFFFAOYSA-N| RTECS = | MeSHName = | ChEBI = 17632}}| Section2 = {{Chembox Properties! Category !! %NO3 !! %NO3–N !! %KNO3 !! Effects
N3|-}}O=3| Appearance =| Solubility = | ConjugateAcid = Nitric acid}}| Section3 = {{Chembox Hazards| MainHazards =| FlashPt =| AutoignitionPt = }}}}Nitrate is a polyatomic ion with the molecular formula {{chem|NO|3|−}} and a molecular mass of 62.0049 u. Organic compounds that contain the nitrate ester as a functional group (RONO2) are also called nitrates.


The anion is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a formal charge of −1. This results from a combination formal charge in which each of the three oxygens carries a −{{frac|2|3}} charge, whereas the nitrogen carries a +1 charge, all these adding up to formal charge of the polyatomic nitrate ion. This arrangement is commonly used as an example of resonance. Like the isoelectronic carbonate ion, the nitrate ion can be represented by resonance structures:
missing image!
- Nitrate-ion-resonance-2D.png -
Canonical resonance structures for the nitrate ion

Properties and diet

(File:Nitrate-ion-with-partial-charges-2D.png|thumb|150px|The nitrate ion with the partial charges shown)Almost all inorganic nitrate salts are soluble in water at standard temperature and pressure. A common example of an inorganic nitrate salt is potassium nitrate (saltpeter). A rich source of inorganic nitrate in the human body comes from diets rich in leafy green foods, such as spinach and arugula. {{chem|NO|3|−}} (inorganic nitrate) is the viable active component within beetroot juice and other vegetables.Dietary nitrate may be found in cured meats, various leafy vegetables, and drinking water; nitrite consumption is primarily determined by the amount of processed meats eaten, and the concentration of nitrates in these meats. Nitrite and water are converted in the body to nitric oxide, which could reduce hypertension. Anti-hypertensive diets, such as the DASH diet, typically contain high levels of nitrates, which are first reduced to nitrite in the saliva, as detected in saliva testing, prior to forming nitric oxide.JOURNAL, Hord, N. G, Tang, Y., Bryan, N. S, Food sources of nitrates and nitrites: the physiologic context for potential health benefits, American Journal of Clinical Nutrition, 90, 1, 2009, 1–10,weblink 10.3945/ajcn.2008.27131, 19439460,


Nitrate salts are found naturally on earth as large deposits, particularly of nitratine, a major source of sodium nitrate.Nitrites are produced by a number of species of nitrifying bacteria, and the nitrate compounds for gunpowder (see this topic for more) were historically produced, in the absence of mineral nitrate sources, by means of various fermentation processes using urine and dung.Nitrates are found in fertilizers.As a byproduct of lightning strikes in earth's nitrogen-oxygen rich atmosphere, nitric acid is produced when nitrogen dioxide reacts with water vapor.


(File:40mm table tennis ball Celluloid.jpg|thumb|right|253|Table tennis balls are made from celluloid, an organic nitrate.)Nitrates are mainly produced for use as fertilizers in agriculture because of their high solubility and biodegradability. The main nitrate fertilizers are ammonium, sodium, potassium, and calcium salts. Several million kilograms are produced annually for this purpose.Wolfgang Laue, Michael Thiemann, Erich Scheibler, Karl Wilhelm Wiegand "Nitrates and Nitrites" in Ullmann's Encyclopedia of Industrial Chemistry, 2006, Wiley-VCH, Weinheim. {{DOI|10.1002/14356007.a17_265}}The second major application of nitrates is as oxidizing agents, most notably in explosives where the rapid oxidation of carbon compounds liberates large volumes of gases (see gunpowder for an example). Sodium nitrate is used to remove air bubbles from molten glass and some ceramics. Mixtures of the molten salt are used to harden some metals.Explosives and table tennis balls are made from celluloid. In the early 20th century, most motion picture film was made of nitrocellulose, but the intense flammability of the film led to it being replaced with "safety film" by the mid-20th-century.Although nitrites are the nitrogen compound chiefly used in meat curing, nitrates are used in certain specialty curing processes where a long release of nitrite from parent nitrate stores is needed. The use of nitrates in food preservation is controversial. This is due to the potential for the formation of nitrosamines when nitrates are present in high concentrations and the product is cooked at high temperatures.WEB,weblink Curing Food, Edinformatics, 21 February 2010, The effect is seen for red or processed meat, but not for white meat or fish.JOURNAL, Kuhnle GG, Bingham SA, Dietary meat, endogenous nitrosation and colorectal cancer, Biochemical Society Transactions, 35, Pt 5, 1355–1357, 2007,weblink 17956350, 10.1042/BST0351355, JOURNAL, Bingham SA, Hughes R, Cross AJ, Effect of white versus red meat on endogenous N-nitrosation in the human colon and further evidence of a dose response, Journal of Nutrition, 132, 11 Suppl, 3522S-3525S, 2002,weblink 12421881, Potently, the production of carcinogenic nitrosamines may be inhibited by the use of the antioxidants vitamin C and the alpha-tocopherol form of vitamin E during curing.JOURNAL, Parthasarathy DK1, Bryan NS, Sodium nitrite: the "cure" for nitric oxide insufficiency, MEAT SCIENCE, 92, 3, 274–279, 2004, 10.1016/j.meatsci.2012.03.001, 22464105, Under simulated gastric conditions, nitrosothiols rather than nitrosamines are the main nitroso species being formed. The use of either compound is therefore regulated; for example, in the United States, the concentration of nitrates and nitrites is generally limited to 200 ppm or lower. They are considered irreplaceable in the prevention of botulinum poisoning from consumption of cured dry sausages by preventing spore germination.BOOK, Food Safety and Toxicity, John, De Vries, CRC Press, 1997, 978-0-8493-9488-1, 70, ., Research has shown that dietary nitrate supplementation delivers positive results when testing endurance exercise performance.Nicholas McMahon, Michael Leveritt, Toby Pavey "The Effect of Dietary Nitrate Supplementation on Endurance Exercise Performance in Healthy Adults: A Systematic Review and Meta-Analysis" in "Sports Medicine", 2016. {{DOI|10.1007/s40279-016-0617-7}}


The historical standard method of testing for nitrate is the Cadmium Reduction Method, which is reliable and accurate although it is dependent on a toxic metal cadmium and thus not suitable for all applications. An alternative method for nitrate and nitrite analysis is enzymatic reduction using nitrate reductase,JOURNAL, Campbell, Wilbur H., Song, Pengfei, Barbier, Guillaume G., Nitrate reductase for nitrate analysis in water, Environmental Chemistry Letters, 28 March 2006, 4, 2, 69–73, 10.1007/s10311-006-0035-4, WEB, Patton, CJ, Kryskalla, JR, Analytical properties of some commercially available nitrate reductase enzymes evaluated as replacements for cadmium in automated, semiautomated, and manual colorimetric methods for determination of nitrate plus nitrite in water,weblink U.S. Geological Survey Scientific Investigations Report, Report No.: 2013–5033, 366, 2016, Patton CJ, Kryskalla JR. Colorimetric determination of nitrate plus nitrite in water by enzymatic reduction, automated discrete analyzer methods: U.S. Geological Survey Techniques and Methods. 2011. p. 34. which has recently been proposed by the US Environmental Protection Agency as an alternate test procedure for determining nitrate.Federal Register. 2015; 80: 8962. An open source photometer has been developed for this method to accurately detect nitrate in water, soils, forage, etc.Wittbrodt BT, Squires DA, Walbeck J, Campbell E, Campbell WH, Pearce JM. (2015) Open-Source Photometric System for Enzymatic Nitrate Quantification. PLoS ONE 10(8): e0134989. doi: 10.1371/journal.pone.0134989 According to Hackaday this device can be built for US$65 to use this method to quantify nitrate accurately.Simple, Cheap Nitrate Tester is Open Source - HackADayweblink visited 8-14-2015Free nitrate ions in solution can be detected by a nitrate ion selective electrode. Such electrodes function analogously to the pH selective electrode. This response is partially described by the Nernst equation.



Nitrate poisoning can occur through enterohepatic metabolism of nitrate due to nitrite being an intermediate.WEB, The Merck Veterinary Manual, Nitrate and Nitrite Poisoning: Introduction,weblink 2008-12-27, Nitrites oxidize the iron atoms in hemoglobin from ferrous iron(II) to ferric iron(III), rendering it unable to carry oxygen.JOURNAL
, Kim-shapiro, D. B.
, Gladwin, M. T.
, Patel, R. P.
, Hogg, N.
, 2005
, … between nitrite and hemoglobin: the role of nitrite in hemoglobin-mediated hypoxic vasodilation
, Journal of Inorganic Biochemistry
, 99
, 1
, 237–246
, 10.1016/j.jinorgbio.2004.10.034
, 15598504
, This process can lead to generalized lack of oxygen in organ tissue and a dangerous condition called methemoglobinemia. Although nitrite converts to ammonia, if there is more nitrite than can be converted, the animal slowly suffers from a lack of oxygen.WEB,weblink Nitrate Poisoning of Livestock, North Dakota State University, May 2008, October 30, 2013, Stoltenow, Charlie, Greg Lardy, yes, 1–4,

Human health effects

Humans are subject to nitrate toxicity, with infants being especially vulnerable to methemoglobinemia due to nitrate metabolizing triglycerides present at higher concentrations than at other stages of development. Methemoglobinemia in infants is known as blue baby syndrome. Although nitrates in drinking water once were thought to be a contributing factor, there now are significant scientific doubts as to whether there is a causal link.T. M. Addiscott & N. Benjamin: Nitrate and human health, Soil Use and Management, Volume 20, Issue 2, pages 98–104, June 2004A. A. Avery: Infant Methemoglobinemia - Reexamining the Role of Drinking Water Nitrates, Environmental Health Perspectives, Volume 107, Number 7, July 1999 Blue baby syndrome now is thought to be the product of a number of factors, which can include any factor that causes gastric upset, such as diarrhoeal infection, protein intolerance, heavy metal toxicity etc., with nitrates playing a minor role. Nitrates, if a factor in a specific case, would most often be ingested by infants in high nitrate drinking water, however, nitrate exposure also may occur if eating, for instance, vegetables containing high levels of nitrate. Lettuce may contain elevated nitrate under growth conditions such as reduced sunlight, undersupply of the essential micronutrients molybdenum (Mo), and iron (Fe), or high concentrations of nitrate due to reduced assimilation of nitrate in the plant. High levels of nitrate fertilization also contribute to elevated levels of nitrate in the harvested plant.Marschner H 1999 Mineral nutrition of higher plants. Academic Press, London. 889Some adults may be more susceptible to the effects of nitrates than others. The methemoglobin reductase enzyme may be under-produced or absent in certain people who have an inherited mutation.WEB, Washington State Department of Health, Q&A: Nitrate in Drinking Water, DOH-331-214, en, es, 9 June 2013,weblink Such individuals cannot break down methemoglobin so rapidly as those who do have the enzyme, leading to increased circulating levels of methemoglobin (the implication being that their blood is not so oxygen-rich as that of the others). Those with insufficient stomach acid, including some vegetarians and vegans, may also be at risk. It is the increased consumption of green, leafy vegetables that typically accompanies these types of diets, that may lead to increased nitrate intake. A wide variety of medical conditions, including food allergies, asthma,WEB,, GERD and Asthma, September 2, 2009,weblink hepatitis, and gallstones may be linked with low stomach acid; these individuals also may be highly sensitive to the effects of nitrate.Methemoglobinemia may be treated with methylene blue, which reduces ferric iron(III) in affected blood cells back to ferrous iron(II).WEB, Methemoglobinemia,weblink The New York Times, 25 October 2016,

Marine toxicity

File:WOA09 sea-surf NO3 AYool.png|right|thumb|Sea surface nitrate from the World Ocean AtlasWorld Ocean AtlasIn freshwater or estuarine systems close to land, nitrate can reach high levels that can potentially cause the death of fish. While nitrate is much less toxic than ammonia,JOURNAL, Romano, N., Zeng, C., 2007, Acute toxicity of sodium nitrate, potassium nitrate and potassium chloride and their effects on the hemolymph composition and gill structure of early juvenile blue swimmer crabs (Portunus pelagicus, Linnaeus 1758) (Decapoda, Brachyura, Portunidae), Environmental Toxicology and Chemistry, 26, 1955–1962, 10.1897/07-144r.1, levels over 30 ppm of nitrate can inhibit growth, impair the immune system and cause stress in some aquatic species.WEB,weblink Nitrates in the Aquarium,, October 30, 2013, Sharpe, Shirlie, However, in light of inherent problems with past protocols on acute nitrate toxicity experiments, the extent of nitrate toxicity has been the subject of recent debate.JOURNAL, Romano N., Zeng, C., 2007, Effects of potassium on nitrate mediated changes to osmoregulation in marine crabs, Aquatic Toxicology, 85, 202–208, 10.1016/j.aquatox.2007.09.004, 17942166, 3, In most cases of excess nitrate concentrations in aquatic systems, the primary source is surface runoff from agricultural or landscaped areas that have received excess nitrate fertilizer. This is called eutrophication and can lead to algae blooms. As well as leading to water anoxia and dead zones, these blooms may cause other changes to ecosystem function, favouring some groups of organisms over others. As a consequence, as nitrate forms a component of total dissolved solids, they are widely used as an indicator of water quality.Symptoms of nitrate poisoning include increased heart rate and respiration; in advanced cases blood and tissue may turn a blue or brown color. Feed can be tested for nitrate; treatment consists of supplementing or substituting existing supplies with lower nitrate material. Safe levels of nitrate for various types of livestock are as follows:WEB,weblink$department/deptdocs.nsf/all/faq8911, Nitrate Risk in Forage Crops - Frequently Asked Questions, Government of Alberta, Agriculture and Rural Development, October 30, 2013, {| class="wikitable"

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