Sodium dodecyl sulfate

Sodium dodecyl sulfate (SDS or NaDS), sodium laurilsulfate or sodium lauryl sulfate (SLS) is an organic compound with the formula CH3(CH2)11OSO3Na). It is an anionic surfactant used in many cleaning and hygiene products. The salt is of an organosulfate consisting of a 12-carbon tail attached to a sulfate group, giving the material the amphiphilic properties required of a detergent.  Being derived from inexpensive coconut and palm oils, it is a common component of many domestic cleaning products.

Production
SDS is synthesized by treating lauryl alcohol with sulfur trioxide gas, or oleum, or chlorosulfuric acid to produce hydrogen lauryl sulfate. The industrially practiced method typically uses sulfur trioxide gas. The resulting product is then neutralized through the addition of sodium hydroxide or sodium carbonate. Lauryl alcohol is in turn usually derived from either coconut or palm kernel oil by hydrolysis, which liberates their fatty acids, followed by hydrogenation.

Due to this synthesis method, commercially samples of SDS are often a mixture of other alkyl sulfates, dodecyl sulfate being the main component.

Applications
SDS is mainly used in detergents for laundry and many cleaning applications. SDS 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 wash soaps. It is found in toothpastes, shampoos, shaving foams, and bubble bath formulations in part for its thickening effect and its ability to create a lather.

Laboratory applications
It can be used to aid in lysing cells during DNA extraction and for unraveling proteins in SDS-PAGE. Sodium lauryl sulfate, in science referred to as sodium dodecyl sulfate (SDS) or Duponol, is commonly used in preparing proteins for electrophoresis in the SDS-PAGE technique. This compound works by disrupting non-covalent bonds in the proteins, denaturing them, and causing the molecules to lose their native shape (conformation).

This new negative charge is significantly greater than the original charge of that protein. The electrostatic repulsion that is created by binding of SDS causes proteins to unfold into a rod-like shape thereby eliminating differences in shape as a factor for separation in the gel. Sodium lauryl sulfate is probably the most researched anionic surfactant compound. Like all detergent surfactants (including soaps), sodium lauryl sulfate removes oils from the skin, and can cause skin and eye irritation. The critical micelle concentration (CMC) in pure water at 25°C is 0.0082 M, 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%). Aqueous solutions of SDS are also popular for dispersing (or suspending) nanotubes.

Biocide
SDS represent a potentially effective topical microbicide, which can also inhibit and possibly prevent infection by various enveloped and non-enveloped viruses such as the Herpes simplex viruses, HIV, and the Semliki Forest Virus.

Medicinal applications
In medicine, sodium lauryl sulfate is used rectally as a laxative in enemas, and as an excipient on some dissolvable aspirins and other fiber therapy caplets.

Taste alteration
Sodium lauryl sulfate diminishes perception of sweetness, an effect commonly observed after recent use of toothpaste containing this ingredient.

Non-carcinogenicity
SDS is not carcinogenic when either applied directly to skin or consumed. A review of the scientific literature stated "SLS [SDS] was negative in an Ames (bacterial mutation) test, a gene mutation and sister chromatid exchange test in mammalian cells, as well as in an in vivo micronucleus assay in mice. The negative results from in vitro and in vivo studies indicate SDS does not interact with DNA."

Sensitivity
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. In animal studies SDS appears to cause skin and eye irritation.

Aphthous ulcers
A preliminary study suggested SDS in toothpaste caused the recurrence of aphthous ulcers, commonly referred to in some countries as canker sores or white sores. The preliminary study "showed a statistically significant decrease in the number of aphthous ulcers from 14.3 after using the SLS-containing dentifrice to 5.1 ulcers after brushing with the SLS-free dentifrice." A clinical study comparing the incidence of recurrent aphthous ulcers during the use of dentifrices with and without sodium lauryl sulfate supported the findings of an earlier independent study which suggest that use of an SLS-free dentifrice should be considered for individuals who suffer from recurrent aphthous ulcers. A clinical double-blind crossover study found sodium lauryl sulfate had a significantly higher frequency of aphthous ulcers than both cocoamidopropyl betaine or a detergent-free paste, on 30 patients with frequent occurrences of recurrent aphthous ulcers. The clinical double-blind crossover study suggests use of an SLS-free toothpaste for patients with recurrent aphthous ulcers would reduce recurrence. A double-blind crossover trial comparing toothpastes with and without SLS found that it had no significant effect on ulcer patterns. Other studies indicate concerns for about SLS in toothpaste.