Surface active agents or surfactants are extremely common compounds that we encounter in everyday life and have extremely useful applications. Their role or function differs from one application to another they can be for, wetting, emulsifying, dispersion, foaming or antifoaming and can be used in everyday applications such as soaps and detergents. A surface active agent can be described as a compound with two opposing regions, one which is hydrophilic and another that is hydrophobic, due to this nature they will be drawn to the interfaces of two different phases whether that be solid-liquid, air-liquid or liquid-liquid. The dual nature of the surfactant compound results in its migration to the interface where the hydrophobic portion will orientate itself to escape the aqueous solution into the non-aqueous phase, conversely the hydrophilic part of the compound will remain in contact with the aqueous phase. The accumulation of these compounds into this interface reduces the surface tension of the liquid, this property is useful for many different applications in the pharmaceutical industry. In general terms surfactant regions described and represented for illustrative purposes as hydrophilic heads and hydrophobic tails. The structure of these compounds can be generally defined by their hydrophilic head regions in two distinct classifications, ionic and non-ionic. As alluded to in their names ionic surfactants have charged particles as hydrophobic groups and non-ionic do not. Ionic surfactants can be further subdivided into cationic, anionic and zwitterionic depending on the nature of this charge. Surfactant hydrophobic tail regions for each of these distinct groups have a similar make-up in that they are generally made up of a hydrocarbon chain of a given length. The tails can include variations dependent on the amount of saturation of these chains, inclusion of aromatic or other functional groups to tailor the properties for a given application (1).
The polar groups regularly employed in anionic surfactants are sulphur based compounds such as sulphate and sulphonate or phosphate and carboxylate compounds. Along with these negatively charged groups positive counter ions are required within the compounds, commonly sodium for water stability and magnesium for oil solubility (2). An example of a generic anionic surfactant is Sodium Lauryl Sulphate, this molecule has a high solubility in water at room temperature and has a bacterial static effect against gram positive bacteria. These properties lend to applications such as use in pre-operation skin cleansing products and medicated shampoos. Another application is its use in the emulsification of wax (3).