Development of Determining the Critical Micelle Concentration of Surfactants by Simple and Fast Titration Method

Critical micelle concentration (CMC) is a crucial parameter of widely used surfactants and many methods have been developed for CMC determination. However, the current methods for CMC determination, such as conductive, surface tension, fluorometric methods, are tedious, time- and sample-consuming because a series of samples with different concentrations of surfactants are needed to be prepared and measured. Although economical, simple and fast titration method for CMC determination (only one sample and several minutes are needed) was reported using changes in the color/fluorescence of ionic organic dyes, it has not been used in practical CMC determination owing to the disadvantages of these dyes: very narrow application range (only suitable for cationic or anionic surfactants), difficultly identified titration end point, especially using different concentrations (10 – 300 μM) for the same kind surfactants. Here, a C6-unsubstituted tetrahydropyrimidine (THP-T1) was found to possess the unique and excellent...