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Abstract
The experimental results for liquid–liquid equilibrium of poly(vinyl pyrrolidone) (K30) + tri-sodium citrate + guanidine hydrochloride (5 and 10 w/w%) aqueous two-phase system at 25°C and different pH values (6.2, 7.4, and 10.0) were studied. The partition behavior of guanidine hydrochloride is known to be a function of several factors. Some of them such as guanidine hydrochloride concentration, pH, polymer/salt ratio (w/w), size, and slant of the tie-lines (STLs) are investigated in this study. At higher guanidine hydrochloride concentrations, the binodal was observed to displace. The behavior of the tie-line size (TLS) seems to be somehow different from the influence of the polymeric phase. The increase of GuHCl concentration decreased the STLs, but the slant and size of the equilibrium tie-lines increased with the pH of the two-phase system. The viscosity (η), density (ρ), electrical conductivity (k), and refractive index (nD) of the poly(vinyl pyrrolidone) (K30) + tri-sodium citrate + guanidine hydrochloride + water two-phase systems versus pH were investigated. It was observed that the viscosity and density of the aqueous two-phase system is influenced by the TLS. The density changes between the phases (Δρ) and viscosity changes of the phases (Δη) increased with the increase of the TLS. It was found that linear relations exist between the TLS and the interphase density and viscosity changes.