Sodium nitrite: Difference between revisions
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This has implications in [[mutagenesis]] since, for example, a cytosine can be converted into a uracil, or an adenine into a [[hypoxanthine]]. These are [[transition mutations]] of the [[deammination]] type. |
This has implications in [[mutagenesis]] since, for example, a cytosine can be converted into a uracil, or an adenine into a [[hypoxanthine]]. These are [[transition mutations]] of the [[deammination]] type. |
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It is for this reason that natural health practitioners consider sodium nitrite as a potential cancer-causing substance. [http://www.naturalnews.com/011148.html] |
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===Synthetic reagent=== |
===Synthetic reagent=== |
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Revision as of 23:20, 17 May 2009
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| Identifiers | |
|---|---|
| ECHA InfoCard | 100.028.687 |
| EC Number |
|
| E number | E250 (preservatives) |
| RTECS number |
|
| UN number | 1500 |
CompTox Dashboard (EPA)
|
|
| Properties | |
| NaNO2 | |
| Molar mass | 69.00 g/mol |
| Appearance | White solid. |
| Density | 2.2 g/cm3, solid |
| Melting point | 280 °C decomp. |
| 82 g/100 ml (20 °C) | |
| Structure | |
| Trigonal | |
| Hazards | |
| Flash point | Non-flammable |
| Related compounds | |
Other anions
|
Sodium nitrate |
Other cations
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Potassium nitrite Ammonium nitrite |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |
Sodium nitrite, with chemical formula NaNO2, is used as a color fixative and preservative in meats and fish. When pure, it is a white to slight yellowish crystalline powder. It is very soluble in water and is hygroscopic. It is also slowly oxidized by oxygen in the air to sodium nitrate, NaNO3. The compound is a strong oxidizing agent.
It is also used in manufacturing diazo dyes, nitroso compounds, and other organic compounds; in dyeing and printing textile fabrics and bleaching fibers; in photography; as a laboratory reagent and a corrosion inhibitor; in metal coatings for phosphatizing and detinning; and in the manufacture of rubber chemicals. It may also be used as an electrolyte in electrochemical grinding manufacturing processes, typically diluted to about 10% concentration in water. Sodium nitrite also has been used in human and veterinary medicine as a vasodilator, a bronchodilator, and an antidote for cyanide poisoning.
Uses
Food additive
As a food additive, it serves a dual purpose in the food industry since it both alters the color of preserved fish and meats and also prevents growth of Clostridium botulinum, the bacteria which causes botulism. In the European Union it may be used only as a mixture with salt containing at most 0.6% sodium nitrite. It has the E number E250. Potassium nitrite (E249) is used in the same way.
While this chemical will prevent the growth of bacteria, it can be toxic in high amounts for animals, including humans. Sodium nitrite's LD50 in rats is 180 mg/kg and its human LDLo is 71 mg/kg, meaning a 65 kg person would likely have to consume at least 4.615 g to result in toxicity.[1] To prevent toxicity, sodium nitrite sold as a food additive is dyed bright pink to avoid mistaking it for something else.
A principal concern of sodium nitrite is the formation of carcinogenic nitrosamines in sodium nitrite containing meats exposed to high temperatures. Sodium nitrite's usage is carefully regulated in the production of cured products in the United States as the concentration in finished products is limited to 200 ppm, and is usually lower. In about 1970, it was found that ascorbic acid (vitamin C), an antioxidant, inhibited nitrosamine formation. [citation needed] Consequently, the addition of at least 550 ppm of ascorbic acid is required in meats manufactured in the United States. Manufacturers sometimes instead use erythorbic acid, a cheaper but equally effective isomer of ascorbic acid. Additionally, manufactures may include alpha-tocopherol (vitamin E) to further inhibit nitrosamine production. Alpha-tocopherol, ascorbic acid, and erythorbic acid all inhibit nitrosamine production by their oxidation-reduction properties. Ascorbic acid for example, forms dehydroascorbic acid when oxidized, which when in the presence of nitrous anhydride, a potent nitrosating agent formed from sodium nitrate, reduces the nitrous anhydride into the nitric oxide gas.[2]
Sodium nitrite consumption has also been linked to triggering migraines in individuals who already suffer from them.[3]
A recent study has found a link between frequent ingestion of cured meats and the COPD form of lung disease. The study's researchers suggest that the high amount of nitrites in the meats was responsible, however the team did not prove the nitrite theory. Additionally, the study doesn't prove that nitrites or cured meat caused higher rates of COPD, merely a link. The researchers did adjust for many of COPD's risk factors, but they commented they can't rule out all possible unmeasurable causes or risks for COPD.[4][5]
Disease treatment
Recently, sodium nitrite has been found to be an effective means to increase blood flow by dilating blood vessels, acting as a vasodilator. Research is ongoing to investigate its applicability towards treatments for sickle cell anemia, cyanide poisoning, heart attacks, brain aneurysms, and pulmonary hypertension in infants.[6][7]
Nitrite as a mutagen
Sodium nitrite produce by bacteria in the gut can become hydrolysed in the acidic environment of the stomach, producing nitrous acid. Nitrous acid reacts with primary amines (such as those found on adenine, guanine and cytosine bases of DNA) producing a nitrose intermediate, which subsequently tautomerises into the enol form. Condensation of this produces a diazonium cation, which is readily converted into an alcohol with the elimination of N2. The resulting alcohol undergoes tautomerisation again, this time resulting in a ketone. Overall this changes R-NH2 into R=O.
This has implications in mutagenesis since, for example, a cytosine can be converted into a uracil, or an adenine into a hypoxanthine. These are transition mutations of the deammination type.
It is for this reason that natural health practitioners consider sodium nitrite as a potential cancer-causing substance. [1]
Synthetic reagent
Sodium nitrite is used to convert amines into diazo compounds. The synthetic utility of such a reaction is to render the amino group labile for nucleophilic substitution, as the N2 group is a better leaving group.
In the laboratory, sodium nitrite is also used to destroy excess sodium azide.[8][9]
- NaNO2 + H2SO4 → HNO2 + NaHSO4
- 2 NaN3 + 2 HNO2 → 3 N2 + 2 NO + 2 NaOH
References
- ^ http://msds.chem.ox.ac.uk/SO/sodium_nitrite.html
- ^ http://lpi.oregonstate.edu/f-w00/nitrosamine.html Nitrosamines and Cancer by Richard A. Scanlan, Ph.D.
- ^ "Heading Off Migraine Pain". FDA Consumer magazine. U.S. Food and Drug Administration. 1998.
- ^ Miranda Hitti (17 April 2007). "Study: Cured Meats, COPD May Be Linked". WebMD Medical News.
- ^ http://ajrccm.atsjournals.org/cgi/content/abstract/175/8/798 Cured Meat Consumption, Lung Function, and Chronic Obstructive Pulmonary Disease among United States Adults - Jiang et al. 175 (8): 798 - American Journal of Respiratory and Critical Care Medicine
- ^ Associated Press (9/5/2005). "Hot dog preservative could be disease cure".
{{cite news}}: Check date values in:|date=(help) - ^ Roxanne Khamsi (27 January 2006). "Food preservative fights cystic fibrosis complication". NewScientist.com.
- ^ "Sodium Azide". Hazardous Waste Management. Northeastern University. 2003.
{{cite web}}: Unknown parameter|month=ignored (help) - ^ Committee on Prudent Practices for Handling, Storage, and Disposal of Chemicals in Laboratories, Board on Chemical Sciences and Technology, Commission on Physical Sciences, Mathematics, and Applications, National Research Council. (1995). Prudent practices in the laboratory: handling and disposal of chemicals. National Academy Press. ISBN 0309052297.
{{cite book}}: Unknown parameter|city=ignored (|location=suggested) (help)CS1 maint: multiple names: authors list (link)
External links
- Organic Consumers Association: Why Processed Meats Are Dangerous to Your Health
- Junkfood Science: Does banning hotdogs and bacon make sense?
- ATSDR - Case Studies in Environmental Medicine - Nitrate/Nitrite Toxicity U.S. Department of Health and Human Services (public domain)
- International Chemical Safety Card 1120.
- European Chemicals Bureau.
- National Center for Home Food Preservation Nitrates and Nitrites.
- TR-495: Toxicology and Carcinogenesis Studies of Sodium Nitrite (CAS NO. 7632-00-0) Drinking Water Studies in F344/N Rats and B6C3F1 Mice.
- FOX news article concerning carcinogicity and hot dogs