Manit Ruiimethabhas and prapin Wilairat Mahldol University Rama 6 Road Bangkok. Thailand
I Determination of Critical Micelle I Concentration Using Acridine Orange Dye Probe I
An Undergraduate Experiment
In recent years, there has heen considerable interest in the studies of micellar properties (14).This is due in part to the increasingly important role of micellar catalysis and application of micelles as model systems for the mode of action of carcinoeens ,. (2). . . Even more recentlv. ..a oaDer . . on micellar effects on reaction rates has appeared in rhis Journal (,5I. It is therefore desirable to introduce students tu,and to t'amiliariz~ them with, some basic concepts of micelles. Several methods have been used to determine the critical micelle concentrations (CMC's) of surfactants dissolved in aqueous solution. For exam~le,direct measurements of some physical propertics such asconductivity and surface tension (6')have been used. Other merhods make uw of additives such as dyes (2) and other types of organic compounds ( 4 ) as probes, so that the CMC of a surfactant solution can he determined by uv-visible spectrophotometric or spectroflnorometric measurements. The nresent method emnlovs the measurements of ahsorhance and fluorescence emission of acridine orange dye (AO) in various concentrations of sodium dodecvl sulfate (SDS) solution. In or near the region of the CMC of SDS there is a s h a r ~ chanee in absorbance and fluorescence of the solution. It has be
