ABSTRACT
Amphoteric surfactants comprise a broad range of compounds that, depending on pH or in-use conditions, display noionic, cationic, or even anionic tendencies; their charge changes as a function of the pH value of the formulation in which they are used. Betaines, imidazoline-derived amphoacetates, alkyl amino propionates, and glycinates are generally included in this category. They are generally regarded as mild surfactants, but this is not a simple matter and may not always be true; when they build complexes in combination with anionic surfactants, these complexes are milder than the individual surfactants [1]. Amphoteric surfactants have the ability to reduce the surface tension of water, as do all other surfactants. The reduction of surface tension depends on the pH of the solution. At pH 6, close to the isoelectric point of most amphoteric surfactants, the net charge of the molecule is zero, which allows for closer packing of surfactant molecules at the interface and produces a great reduction of surface tension.
