Critical micelle concentration of non-ionic surfactants by polaro-graphic and spectrophotometric methods-A comparative study

The polarographic micelle point (PMP) values of non-ionic surfactants, viz., Nonidet P40, Nonidet P42 and Nonex 501 have been determined by a polarographic maximum suppression method in the presence of electrolytes (used for polarographic reduction) and compared with the critical micelle concentration (c.m.c.) values of nonionic surfactants obtained by other methods (spectrophotometric and electrocapillary curves methods). The PMP values are always lower than those obtained by other methods. The difference in c.m.c. values is due to the presence of ions of depolarizer and supporting electrolytes. The presence of electrolytes is likely to influence the water structure, thereby causing a lowering in c.m.c. values.