DETERMINATION OF CRITICAL MICELLE CONCENTRATION OF ANIONIC SURFACTANTS - COMPARISON OF INTERNAL AND EXTERNAL FLUORESCENT-PROBES

Fluorescence spectroscopy has been utilized to determine the critical micelle concentrations (CMC) of anionic surfactants by external and in ternal probes and the results have been compared to those obtained by the surface tension method. The selection of anionic surfactants gave us the flexibility of having the probe within the surfactant molecule and having it reside at the palisade layer or in the micellar core. It is shown that the CMC value is not affected by the nature (whether pa rt of the surfactant molecule or externally added) and location of the probe within the micelle. CMC values determined by surface tension an d fluorescence techniques using external and internal probes agree qui te well in linear alkylbenzene sulfonate (LAS) and secondary alkyl sul fonate (SAS) systems. (C) 1997 Academic Press.