Determination of Critical Micellar Concentration of CTAB in Mixed Medium of Water and Organic Solvent with Ion-Selective Electrode

Ion-selective electrode (ISE) of cationic surfactant with cetyltrimethylammonium bromide-tetraphenylboron as electroactive substance, was prepared and its property tested. Good Nernst response of the ISE was observed against the cationic surfactant cetyltrimethylammonium bromide(CTAB)and linear response range of the ISE was kept in the range of 1×10-6-1×10-3mol·L-1. The electrode was used in the determination of critical micellar concentration (CMC) of CTAB in water/organic solvent mixed medium, the results obtained were consistent with those found by conductivity method. Magnitude of CMC of CTAB solution was increased by addition of polar organic solvent and increased to a greater extent upon addition of more organic solvent. Smaller the value of dielectric constant of the polar organic solvent added, greater will be the CMC value attained.