Association Behavior of 3,4-Dihydroxy-9,10-dioxo-2-anthracenesulfonic Acid Sodium Salt in Cationic Surfactant Medium Under Different pH Conditions

Abstract

Ultraviolet (UV)-visible behavior of 3,4-dihydroxy-9,10-dioxo-2-anthracenesulfonic acid sodium salt (ARS) has been studied at pH 4.0, aqueous medium, and at pH 10.0. The effects of cetyl trimethylammoniumbromide (CTAB) on the UV-visible spectra of ARS have been evaluated qualitatively as well as quantitatively in the different concentration regions of CTAB. The shift in the UV-visible spectrum of ARS, due to CTAB, at its low concentration is comparable to the shift shown by the same at pH 10.0. In acidic and basic pH, effect of CTAB is significantly lowered on the UV-visible spectra than ARS in the purely aqueous medium. In aqueous and basic medium, lower values of partition and binding constant are obtained compared to the one obtained in acidic medium. Conductivity studies show that increasing dye concentrations have no effect on its partitioning behavior nevertheless critical micelle concentration of CTAB is lowered.

Keywords:

• Alizarin red S
• cationic surfactant
• complexation
• pH
• UV-visible spectroscopy