Sodium dodecyl sulfate
Sodium dodecyl sulfate (SDS or NaDS) (CH3(CH2)11OSO3Na) (FW 288.38), also known as sodium lauryl sulfate (SLS), is an ionic detergent that is used in household products such as toothpastes, shampoos, shaving foams and bubble baths for its thickening effect and its ability to create a lather. The molecule has a tail of 12 carbon atoms, attached to a sulfate group, giving the molecule the amphiphilic properties required of a detergent.
It is prepared by sulphation of lauryl alcohol (1-dodecanol, dodecyl alcohol, CH3(CH2)10CH2OH) followed by neutralisation with sodium carbonate. It is used in both industrially produced and home-made cosmetics.
Like all detergents (as opposed to true soaps), it removes natural oils from the skin, and can therefore cause skin irritation. It is particularly irritating to the eyes.
SLS can be converted by ethoxylation to sodium laureth sulphate (also called sodium lauryl ether sulphate; SLES), which is less harsh on the skin.
In laboratories, SDS is commonly used in gel electrophoresis (SDS-PAGE), where its detergent properties help keep the proteins being studied in a denatured state.
The critical micelle concentration in pure water is 0.0085 M, and the aggregation number at this concentration is around 50.
