Mixed micelle formation of cationic gemini surfactant with anionic bile salt: a PAH solubilization study

Abstract

Aqueous mixed micelle formation between cationic gemini surfactant (butanediyl-1,4-bis (N,N-alkyl ammonium) dibromide, m-4-m; or ethane-1,2-diyl (N,N-dimethyl-N-dodecyl-alkyl ammoniumacetoamide) dichloride, m-Eda-m, where m=12,14 and 16) and bile salt (sodium cholate, SC or sodium deoxycholate, SDC) has been investigated by conductivity measurements and the critical micelle concentration values are compared with individual gemini surfactant or bile salt. Surfactant–bile salt interactions (interaction parameter, βm) have been compared using theoretical models of Clint, Rubingh and Motomura. cmc values, with varying mole fractions of CG or bile salt, were used to obtain composition of binary mixture for PAH solubilization. Solubilization studies of polycyclic aromatic hydrocarbons PAHs, fluorene, anthracene and pyrene, have also been performed spectrophotometrically in aqueous cationic gemini (CG) with or without bile salt (SC or SDC). Individual bile salt nearly failed to solubilize any amount of PAHs. The solubilization potential has been discussed in the light of molar solubilization ratio (MSR) and compared with other similar CG-anionic surfactant systems. This is the first study in which oppositely charged CG-bile salt binary mixtures are used to enhance aqueous solubility of PAHs. The study may find potential use in biomedical applications.