Fluorometric analysis of micelle formation of sodium dodecyl sulfate.

Abstract

The micelle formation of sodium dodecyl sulfate (SDS) was studied using pyrene as a fluorescence probe. The critical micelle concentration (CMC) of SDS was estimated to be 8 mM from the changes in monomer fluorescence intensity and ratio of fluorescence intensities at 392 and 375 nm, in good agreement with the reported values obtained from different methods. The results of measurements of excimer fluorescence and fluorescence polarization suggested that the small aggregates of SDS molecules are formed in their low concentrations below the CMC and that the flexibility of hydrocarbon chains in soap molecules is remarkably reduced by growing from aggregates to micelles. The difference in arrangement of hydrocarbon chains between the premicellar and micellar states were manifested also by the different responses of fluorescence parameters of pyrene to MgCl2 and temperature in low and high concentrations of SDS.