Spectral Studies of Eriochrome Black T in Cationic Surfactants

The critical micelle concentration (CMC) for a series of cationic surfactants N-Alkyltrimethylammonium i.e. (CnTAC, n=12, 14, 16, 18) have been determined by electrical conductivity and surface tension methods. The interaction of anionic dye Eriochrome Black T (EBT) with cetyl-trimethylammonium chloride and cetylpyridinium chloride (CPC) has been investigated spectrophotometrically. The binding constant (Kb) and the surface excess (Γ) were calculated. The results show that with increasing the surfactants alkyl chain lengths, CMC and minimum area (Amin) decreases, while the surface excess concentrations increase. It has been found that the binding constant of CPC is double - fold that than of the binding constant of cetyl-trimethylammonium chloride (C16TAC).