(162ag) A Novel Approach to Determine Critical Micelle Concentration of Surfactant Based on the First Derivative Treatment of Fluorescence Characteristics of Pyrene

Boltzmann-fitting treatment of fluorescence characteristics of pyrene probe in aqueous surfactant solution has been used for determining the critical micelle concentration ( cmc) of surfactants. In this paper, a novel approach based on the first derivative treatment of fluorescence characteristics of pyrene was established to determine cmc . In the curves of I₃/I₁ and I₅/I₁ ratio vs surfactant concentration obtained from fluorescence spectrum of pyrene solution, we located the cmc values at the concentrations corresponding to the maximum value of the first derivatives. Comparing with that from Boltzmann-fitting treatment, the first derivative approach does not need to assume the types of the fluorescence curves or choose the break points subjectively. This first derivative approach was validated by eight kinds of typical ionic and nonionic surfactants. The cmc values of anionic and cationic surfactants determined with first derivative approach were in good agreement with the documented cmc value obtained from surface tension method, while for cmc values of nonionic surfactants assayed, positives deviation was found.