New amphoteric surfactants containing a phosphoric acid group: II. Binary system of amphoteric/anionic surfactant of sodium 2‐(N‐2‐hydroxytetradecyl‐N‐methylamino)ethyl hydrogen phosphate

We studied behaviors of the binary system of 2‐(N‐2‐hydroxytetradecyl‐N‐methylamino)ethyl hydrogen phosphate (C 14 ‐HMP) and sodium dodecyl sulfate (SDS) in aqueous solution. We found that C 14 ‐HMP reduced the ability of SDS to denature protein, to inhibit enzyme activity and to decrease transepidermal water loss. These phenomena were considered to be due to the interaction between the cationic group in the zwitterionic structure of C 14 ‐HMP and the anionic group of sulfate in SDS molecule. These behaviors suggest that C 14 ‐HMP has a potential to reduce skin irritation when applied to personal care products such as cleaners and shampoos having anionic surfactants.