Collect. Czech. Chem. Commun. 1989, 54, 622-632

Spectrophotometric investigation of interactions of sulfophthalein dyes with surfactants

Vlastimil Kubáň, Josef Hedbávný, Irena Jančářová and Milan Vrchlabský

Department of Analytical Chemistry, J. E. Purkyně University, 611 37 Brno


The effect of cationic (hexadecylpyridinium bromide, hexadecyltrimethylammonium bromide, Septonex), anionic (sodium dodecyl sulfate) and nonionic (Brij 35, Triton X-100) surfactants on the deprotonation of the phenolic oxygen in bromophenol red, bromophenol blue and bromocresol green is studied. The conditional dissociation constants Kai* depend on the surfactant concentration and, in the alkylpyridinium surfactant series, on the alkyl chain length at a constant concentration of inert electrolyte, and on the concentration of the inert electrolyte (Cl-, Br-, NO3-, SO42-, H2PO4-, CH3COO-, HCOO-, ClO4-) or of the sulfophthalein dye at a constant concentration of a cationic surfactant. In acid and alkaline solutions, cationic surfactants (tensides, T) and the dyes (H2L) form ionic associates with the stoichiometric composition {T+, LH-} and {T2+, L2-}, respectively, exhibiting absorption maxima at 400-430 nm (ε = 1.3-2.0 m2 mmol-1) and at 570-630 nm (ε = 3.5-4.5 m2 mmol-1), respectively, formation of these associates was confirmed for chloroform extracts by the continuous variations and molar ratios methods.