Two‐phase mixed indicator method for the determination of zwitterionic surfactants

Abstract

Abstract The two‐phase, mixed indicator method for anionic surfactants has been modified and applied to zwitterionic surfactants. The modifications entail: (i) lowering the pH; (ii) adding 95% ethanol, and (iii) increasing the concentration of mixed indicator solution and adjusting the ratio of the indicators. By adjusting one parameter (the amount of 95% ethanol added), the method is applicable to different types of zwitterionic surfactants. Six different surfactants were examined; three were pure materials synthesized and purified in our laboratory, and the remaining three were commercial materials.