Studies on the interaction of surfactants with cationic dye by absorption spectroscopy

The interaction of methyl violet, a cationic dye, with various surfactants, viz. anionic (SDS), nonionic (Triton X-100), and cationic (CTAB), has been investigated spectrophotometrically in submicellar and micellar concentration range. While in the submicellar concentration region of SDS the higher aggregates of the dye are found, in the micellar concentration region the monomer of the dye predominates. With nonionic surfactant the dye is solubilized primarily as the monomer. CTAB produces no perturbation to the visible spectra of the dye. In the presence of strong electrolytes such as NaNO3 and NaCl the dye aggregates are formed at a much lower SDS concentrations. (C) 2000 Academic Press.