Phase separation and thermodynamics of the mixture of metformin hydrochloride + triton X-100 in ammonium salts media: impacts of composition of media

Abstract

Cloud point (CP)/lower consolute temperature (LCT) of aqueous mixture of TX-100 and a highly recognised anti-diabetic drug metformin hydrochloride (MNH) was analysed in absence/presence of NH4Cl, NH4NO3, (NH4)2SO4 and (NH4)2HPO4. The CP values were found to be decreased with increasing concentrations of ammonium salts. Occurrence of aggregation in respective solution systems might result in declining of corresponding CP. Thermodynamic parameters (ΔGc0, ΔHc0 and ΔSc0) were calculated at CP. The appearance of positive values of Gibbs free energy (ΔGc0) indicates that clouding in the studied system was thermodynamically non-spontaneous and the degree of non-spontaneity was diminished with increasing in the extents of electrolytes. The computed enthalpy (ΔHc0) and entropy (ΔSc0) values of the system showed negative values in cases of aq. NH4Cl, (NH4)2SO4 and (NH4)2HPO4 while the negative values tend to reduce with rise of electrolytes content. In case of aq. NH4NO3 medium, the reverse results for the ΔHc0 and ΔSc0 values were detected. The ΔHc0 and ΔSc0 values in the studied system indicate the presence of electrostatic interaction between TX-100 and MNH in NH4Cl, (NH4)2SO4, (NH4)2HPO4 media whereas the hydrophobic interactivity might play a great role within the mixture when it was placed in the NH4NO3 solution.