Effect of different additives on the phase separation behavior and thermodynamics of p-tert-alkylphenoxy poly (oxyethylene) ether in absence and presence of drug

Cloud point (CP) determinations of 4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (TX-100 (nonionic surfactant)) was carried out in aqueous as well as in the attendance of drug (ceftriaxone sodium trihydrate (CFT))/(CFT + different inorganic salts) and discussed thoroughly. Nonionic surfactants are employed extensively in different formulations. In aqueous solution, the values of CP of TX-100 are obtained to increase by means of enhancing of their concentration in the solution. The CP values of TX-100 solutions were found to decrease in the presence of drug and their values decrease more with rising concentrations of the drug. The values of CP of CFT and TX-100 mixtures were found to further decrease in the attendance of inorganic salts in comparison to their absence. The effect of different sodium salts in decreasing CP values of TX-100 was achieved in the following order:NaCO₃ > Na₂SO₄ > NaCl. However, in the case of potassium and ammonium salts, the decreasing order obtained is K₂SO₄ > KCO₃ > KCl and (NH₄)₂SO₄ > Na₂CO₃ > NH₄Cl respectively. Various thermodynamic parameters for example standard free energy (ΔG_c^Θ), standard enthalpy (ΔH_c^Θ) as well as standard entropy (ΔS_c^Θ) changes of phase separation were also evaluated and discussed in detail on the basis of their behavior.