Sodium dodecyl sulfate
Sodium dodecyl sulfate
Sodium monododecyl sulfate; Sodium lauryl sulfate; Sodium monolauryl sulfate; Sodium dodecanesulfate; Sodium coco-sulfate; dodecyl alcohol, hydrogen sulfate, sodium salt; n-dodecyl sulfate sodium; Sulfuric acid monododecyl ester sodium salt;
3D model (JSmol)
|E number||E487 (thickeners, ...)|
CompTox Dashboard (EPA)
|Molar mass||288.372 g/mol|
|Appearance||white or cream-colored solid|
|Melting point||206 °C (403 °F; 479 K)|
|8.2 mM at 25 °C|
Refractive index (nD)
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|1288 mg/kg (rat, oral)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Sodium dodecyl sulfate (SDS) or sodium lauryl sulfate (SLS), sometimes written sodium laurilsulfate, is a synthetic organic compound with the formula CH3(CH2)11SO4Na. It is an anionic surfactant used in many cleaning and hygiene products. This molecule is an organosulfate and a salt. It consists of a 12-carbon tail attached to a sulfate group, that is, it is the sodium salt of dodecyl hydrogen sulfate, the ester of dodecyl alcohol and sulfuric acid. Its hydrocarbon tail combined with a polar "headgroup" give the compound amphiphilic properties and so make it useful as a detergent.[not verified in body] Also derived as a component of mixtures produced from inexpensive coconut and palm oils, SDS is a common component of many domestic cleaning, personal hygiene and cosmetic, pharmaceutical, and food products, as well as of industrial and commercial cleaning and product formulations.[not verified in body]
Structure and properties
SDS is in the family of organosulfate compounds, and has the formula, CH3(CH2)11SO4Na. It consists of a 12-carbon tail attached to a sulfate group, that is, it is the sodium salt of a 12-carbon alcohol that has been esterified to sulfuric acid. An alternative description is that it is an alkyl group with a pendant, terminal sulfate group attached. As a result of its hydrocarbon tail, and its anionic "head group", it has amphiphilic properties that allow it to form micelles, and so act as a detergent.
The critical micelle concentration (CMC) in pure water at 25 °C is 8.2 mM, and the aggregation number at this concentration is usually considered to be about 62. The micelle ionization fraction (α) is around 0.3 (or 30%).
SDS is synthesized by treating lauryl alcohol with sulfur trioxide gas, oleum, or chlorosulfuric acid to produce hydrogen lauryl sulfate. The resulting product is then neutralized through the addition of sodium hydroxide or sodium carbonate. Lauryl alcohol can be used in pure form or may be derived from either coconut or palm kernel oil by hydrolysis (which liberates their fatty acids), followed by hydrogenation. When produced from these sources, commercial samples of these "SDS" products are actually not pure SDS, rather a mixture of various sodium alkyl sulfates with SDS being the main component. For instance, SDS is a component, along with other chain-length amphiphiles, when produced from coconut oil, and is known as sodium coco sulfate (SCS). SDS is available commercially in powder, pellet, and other forms (each differing in rates of dissolution), as well as in aqueous solutions of varying concentrations.
Cleaning and hygiene
SDS is mainly used in detergents for laundry with many cleaning applications. It is a highly effective surfactant and is used in any task requiring the removal of oily stains and residues; for example, it is found in higher concentrations with industrial products including engine degreasers, floor cleaners, and car exterior cleaners.
In lower concentrations, it is found in hand soap, toothpastes, shampoos, shaving creams, and bubble bath formulations, for its ability to create a foam (lather), for its surfactant properties, and in part for its thickening effect.
This section needs expansion with: a secondary source-derived summary of its uses in food and related products, as this is a clear more preeminent application than many of those that follow. You can help by adding to it. (March 2016)
Sodium dodecyl sulfate, appearing as its synonym sodium lauryl sulfate (SLS), is considered a generally recognized as safe (GRAS) ingredient for food use according to the USFDA (21 CFR 172.822). It is used as an emulsifying agent and whipping aid. SLS is reported to temporarily diminish perception of sweetness.
Sodium lauryl sulfate, in science referred to as sodium dodecyl sulfate (SDS), is used in cleaning procedures, and is commonly used as a component for lysing cells during RNA extraction and/or DNA extraction, and for denaturing proteins in preparation for electrophoresis in the SDS-PAGE technique.
In the case of the SDS-PAGE application, the compound works by disrupting non-covalent bonds in the proteins, and so denaturing them, i.e., causing the protein molecules to lose their native conformations and shapes. By binding to the proteins with high affinity and in high concentrations, the negatively charged detergent provides all proteins with a similar net negative charge and therefore a similar charge-to-mass ratio. In this way, the difference in mobility of the polypeptide chains in the gel can be attributed solely to their size as opposed to both their size and charge. It is possible to make separation based on the size of the polypeptide chain to simplify the analysis of protein molecules, this can be achieved by denaturing proteins with the detergent SDS. The association of SDS molecules with protein molecules imparts an associated negative charge to the molecular aggregate formed; this negative charge is significantly greater than the original charge of that protein. The electrostatic repulsion that is created by SDS binding forces proteins into a rod-like shape, thereby eliminating differences in shape as a factor for electrophoretic separation in gels. A dodecyl sulfate molecule has two negative charges at the pH value used for electrophoresis, this will lead the net charge of coated polypeptide chains to be much more negative than uncoated chains. The charge-to-mass ratio is essentially identical for different proteins because SDS coating dominates the charge.
SDS is used in an improved technique for preparing brain tissues for study by optical microscopy. The technique, which has been branded as CLARITY, was the work of Karl Deisseroth and coworkers at Stanford University, and involves infusion of the organ with an acrylamide solution to bind the macromolecules of the organ (proteins, nucleic acids, etc.), followed by thermal polymerization to form a "brain–hydrogel" (a mesh interspersed throughout the tissue to fix the macromolecules and other structures in space), and then by lipid removal using SDS to eliminate light scattering with minimal protein loss, rendering the tissue quasi-transparent.
SDS has been proposed as a potentially effective topical microbicide, for intravaginal use, to inhibit and possibly prevent infection by various enveloped and non-enveloped viruses such as the herpes simplex viruses, HIV, and the Semliki Forest virus.
In gas hydrate formation experiments, SDS is used as a gas hydrate growth promoter. Researchers aim for gas hydrate promotions as scale-up of industrial applications of gas hydrates such as desalination process, gas storage, and gas separation technologies.
Liquid membranes formed from SDS in water have been demonstrated to work as unusual particle separators. The device acts as a reverse filter, allowing large particles to pass while capturing smaller particles.
SDS is not carcinogenic when consumed or applied directly, even to amounts and concentrations that exceed amounts used in standard commercial products. The earlier review of the Cosmetic Ingredient Review (CIR) program Expert Panel in 1983 reported that SDS (there, abbreviated SLS, for sodium lauryl sulfate) in concentrations up to 2%, in a year-long oral dietary studies in dogs, gave no evidence of tumorigenicity or carcinogenicity, and that no excess chromosomal aberrations or clastogenic effects were observed in rats fed up to 1.13% sodium lauryl sulfate in their diets for 90 days, over those on a control diet.:157, 175 The 2005 review by the same group indicated that further available data lacked any available suggestion that SDS or the related ammonium salt of the same amphiphile could be carcinogenic, stating that "Despite assertions to the contrary on the Internet, the carcinogenicity of these ingredients is only a rumor;" both studies conclude that SDS appears "to be safe in formulations designed for discontinuous, brief use followed by thorough rinsing from the surface of the skin. In products intended for prolonged contact with skin, concentrations should not exceed 1%.":89ff
Like all detergents, sodium lauryl sulfate removes oils from the skin, and can cause skin and eye irritation. It has been shown to irritate the skin of the face, with prolonged and constant exposure (more than an hour) in young adults. SDS may worsen skin problems in individuals with chronic skin hypersensitivity, with some people being affected more than others.
The low cost of SDS, its lack of impact on taste, its potential impact on volatile sulfur compounds (VSCs), which contribute to malodorous breath, and its desirable action as a foaming agent have led to the use of SDS in the formulations of toothpastes. A series of small crossover studies (25-34 patients) have supported the efficacy of SLS in the reduction of VSCs, and its related positive impact on breath malodor, although these studies have been generally noted to reflect technical challenges in the control of study design variables. While primary sources from the group of Irma Rantanen at University of Turku, Finland conclude an impact on dry mouth (xerostomia) from SLS-containing pastes, a 2011 Cochrane review of these studies, and of the more general area, concludes that there "is no strong evidence… that any topical therapy is effective for relieving the symptom of dry mouth." A safety concern has been raised on the basis of several studies regarding the effect of toothpaste SDS on aphthous ulcers, commonly referred to as canker or white sores. A consensus regarding practice (or change in practice) has not appeared as a result of the studies. As Lippert notes, of 2013, "very few… marketed toothpastes contain a surfactant other than SLS [SDS]," and leading manufacturers continue to formulate their produce with SDS.
Interaction with fluoride
Some studies have suggested that SLS in toothpaste may decrease the effectiveness of fluoride at preventing dental caries (cavities). This may be due to SLS interacting with the deposition of fluoride on tooth enamel.
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Obtaining high-resolution information from a complex system, while maintaining the global perspective needed to understand system function, represents a key challenge in biology. Here we address this challenge with a method (termed CLARITY) for the transformation of intact tissue into a nanoporous hydrogel-hybridized form (crosslinked to a three-dimensional network of hydrophilic polymers) that is fully assembled but optically transparent and macromolecule-permeable.
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[Quoting:] Carcinogenesis. A one-year chronic oral study using beagles showed that Sodium Lauryl Sulfate at concentrations up to 2% in the diet was not tumorigenic or carcinogenic. [p. 157] / Summary… In mutagenesis studies, rats fed 1.13% and 0.56% Sodium Lauryl Sulfate in the diet for 90 days produced no more chromosomal aberrations or clastogenic effects than did a control diet. [p. 175]. / Conclusion. Sodium Lauryl Sulfate and Ammonium Lauryl Sulfate appear to be safe in formulations designed for discontinuous, brief use followed by thorough rinsing from the surface of the skin. In products intended for prolonged contact with skin, concentrations should not exceed 1%. [p. 176.].
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[Quoting:] Sodium Lauryl Sulfate and Ammonium Lauryl Sulfate appear to be safe in formulations designed for discontinuous, brief use followed by thorough rinsing from the surface of the skin. In products intended for prolonged contact with skin, concentrations should not exceed 1%… New studies confirmed the irritant properties of these ingredients and reinforced the concentration limit of 1% or leave-on uses established by the [earlier] Panel. [p. 89] / The available studies that looked for carcinogenesis failed to find evidence that Ammonium Lauryl Sulfate are [sic.] carcinogenic. None of the available data suggested that SLS or Ammonium Lauryl Sulfate could be carcinogenic. Despite assertions to the contrary on the Internet, the carcinogenicity of these ingredients is only a rumor. [pp. 89ff]CS1 maint: multiple names: authors list (link).
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[Quoting abstract:] There is no strong evidence from this review that any topical therapy is effective for relieving the symptom of dry mouth.See Rantanen, et al. (2003) J. Contemp. Dent. Pract. 4(2):11–23, , and Rantanen, et al. (2003) Swed. Dent. J. 27(1):31–34, , referenced therein.
- No literature evidence could be found, as of March 2016, indicating a consensus of dental medical professionals regarding the published primary results on SDS.[needs update]
- Some of the published studies, from latest to earliest, are as follows. (i) A 2012 double-blind crossover study of 90-patients failed to find a significant difference in number of ulcers between groups using SLS-containing toothpaste, versus a group using an SLS-free toothpaste, but did suggest significant reduction in ulcer duration and improvement in patient pain scores, see Shim, Y. J.; Choi, J. -H.; Ahn, H. -J.; Kwon, J. -S. (2012). "Effect of sodium lauryl sulfate on recurrent aphthous stomatitis: A randomized controlled clinical trial". Oral Diseases. 18 (7): 655–60. doi:10.1111/j.1601-0825.2012.01920.x. PMID 22435470., a study also cited in the Lippert (2013) book chapter. (ii) A 1999 double-blind crossover study of 47 patients failed to find any statistically significant difference in the number, episodes, and duration of such ulcers between these two groups, and of pain scores between them, see Healy CM, Paterson M, Joyston-Bechal S, Williams DM, Thornhill MH (January 1999). "The effect of a sodium lauryl sulfate-free dentifrice on patients with recurrent oral ulceration". Oral Dis. 5 (1): 39–43. doi:10.1111/j.1601-0825.1999.tb00062.x. PMID 10218040. (iii) A 1997 study[clarification needed] suggested a significantly higher number of ulcers after SLS toothpaste use, versus its control group, see Chahine L, Sempson N, Wagoner C (December 1997). "The effect of sodium lauryl sulfate on recurrent aphthous ulcers: a clinical study". Compend. Contin. Educ. Dent. 18 (12): 1238–40. PMID 9656847., a study also cited in the Lippert (2013) book chapter. (iv) A 1996 follow-up 30-patient double-blind crossover study and a 1994 preliminary 10-patient crossover study by the same authors suggested significantly higher numbers of aphthous ulcers after using SLS-containing toothpaste, compared with an SLS-free toothpaste, see Herlofson BB, Barkvoll P (June 1996). "The effect of two toothpaste detergents on the frequency of recurrent aphthous ulcers". Acta Odontol. Scand. 54 (3): 150–53. doi:10.3109/00016359609003515. PMID 8811135. and Herlofson BB, Barkvoll P (October 1994). "Sodium lauryl sulfate and recurrent aphthous ulcers. A preliminary study". Acta Odontol. Scand. 52 (5): 257–59. doi:10.3109/00016359409029036. PMID 7825393.
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