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.

Spectral-luminescent properties of pH-sensitive azo fluorophore in complexes with quaternary ammonium disinfectants

“…Since EHDAB has greater hydrophobic character as compared to CTAB, the former incorporated higher number of AHABA molecules as compared to the latter ( Table 2). The values of n for AHABA are comparable with literature values reported for some anionic molecule partition to cationic micelles [39][40][41][42][43][44]47].…”

“…The values of K x for azo molecule were found comparable with the reported literature values for some azo molecule partition to cationic micelles [40,41,44,47]. The standard free energy change of the transfer (ΔG o p ) of AHABA molecules from bulk aqueous phase to micellar region can be calculated using the following relation: Table 4 Values of n b , K b , K sv , and ΔG b for AHABA in micellar solution of cationic surfactants under different pH at 25 ± 0.1°C Here, T is absolute temperature and R is the gas constant.…”

“…The peak at 446 nm is probably due to the association of the ion of AHABA with the counterion of a surfactant [40,41], which was later checked by differential absorbance measurements. The peak shoulder around 414-422 nm is probably due to the presence of unbound additive molecule that did not involve in ion pairing association.…”

“…To locate the active sites for electrophilic and nucleophilic attack, the relative polarity and reactivity of AHABA molecule/ion were estimated by molecular electrostatic potential (MEP) and frontier molecular orbital (FMO) energy calculations, since MEP and FMO are handy tools to evaluate the structure-reactivity relationship and chemical stability of the molecules [34][35][36][37][38]. Moreover, to get site-specific affinity and biophysical insight into the molecular distribution of AHABA in colloidal fluid, the spectral behavior of this active azo moiety in association with Quats was analyzed by using excitation and emission spectroscopic measurements given that the ionic surfactants have a profound effect on the spectral behavior of numerous organic molecules [39][40][41][42][43][44][45][46][47].…”