Determination of CMC of Surfactants with UV-vis Absorption Spectrophotometry

The critical micelle concentrations of different surfactants(CTAB,As,AOT,C 12 BE,C 14 BE,As-CTAB,and AOT-CTAB mixtures) were determined by using UV-vis absorption spectrphotometry,and the N,N-diethylaniline(DEA) is used to be the ultraviolet absorption probe in the CMC measurements. At the same time,the solubilization site of DEA in a micelle was investigated by 1 H NMR spectra,and it was foud that DEA is solubilized in the core of a micelle. The difference between λ max of DEA at above the CMC approached the value in n-octane and at below the CMC approached the Value in water. The concentration at the distinct break point for the curve of λ max vs surfactant concentrations was the CMC value of surfactant.