Physico‐Chemical Investigation of Clouding Behavior, Thermodynamics, and Interaction Forces for Triton X‐100 and Tetracaine Hydrochloride Mixture: Assessment of Effects of Electrolytes.

Assessment of clouding development and thermodynamic parameters of the surfactant‐drug mixtures are crucial for chemists, industrialists, and researchers because of the numerous possible uses of this combined mixture in the pharmaceutical sectors. Cloud point (CP) of the surfactant triton X‐100 (TX‐100) and tetracaine hydrochloride (TCH) drug mixed system was explored in aqueous and aqueous inorganic salts (NaCl, NaBr, Na2SO4, and Na3PO4) media. In an aqueous medium, an enhanced pattern in the CP values of amphiphile used was observed with rising concentration of TCH drug. On the contrary, the CP values of study mixture were followed to be reduced through the growth of inorganic salts concentration and follows the sequential order as: CPH2O+NaBr>${\mathrm{C}}{{{\mathrm{P}}}_{{{{\mathrm{H}}}_2}{\mathrm{O}} + {\mathrm{NaBr}}}} > $CPH2O+NaCl>CPH2O+Na2SO4>CPH2O+Na3PO4${\mathrm{C}}{{{\mathrm{P}}}_{{{{\mathrm{H}}}_2}{\mathrm{O}} + {\mathrm{NaCl}}}} > {\mathrm{C}}{{{\mathrm{P}}}_{{{{\mathrm{H}}}_2}{\mathrm{O}} + {\mathrm{N}}{{{\mathrm{a}}}_2}{\mathrm{S}}{{{\mathrm{O}}}_4}}} > {\mathrm{C}}{{{\mathrm{P}}}_{{{{\mathrm{H}}}_2}{\mathrm{O}} + {\mathrm{N}}{{{\mathrm{a}}}_3}{\mathrm{P}}{{{\mathrm{O}}}_4}}}$. The decreased CP indicates the reduction of solubility of the investigation system in salts media in comparison to aqueous medium. Different thermodynamic parameters were determined at CP and discussed properly. Entropy (ΔSco${{\Delta}}S_c^o$) and enthalpy (ΔHco${{\Delta}}H_c^o$) values for clouding of TX‐100 + TCH mixtures were obtained positive in aqueous media and negative in electrolytes media. According to the magnitudes of ΔHco${{\Delta}}H_c^o$ and ΔSco${{\Delta}}S_c^o$, the electrostatic and hydrophobic interactions are the main forces operating between TX‐100 and TCH. In this instance, the intrinsic enthalpy (ΔHco,∗$({{\Delta}}H_c^{o,*}$) and compensation temperature (Tc) were assessed, compared, and discussed logically. [ABSTRACT FROM AUTHOR]