Interfacial tension plays a key role in understanding many polymer engineering processes and applications at high pressure. Supercritical fluids are promising media for reducing interfacial tension and increasing the solubility of gas into polymers melts. An experimental technique modified for studies of the interfacial interactions of liquids in equilibrium with gas in a glass-windowed equilibrium cell based on the means of the capillary rise method was applied for the binary systems of CO2 + PEG (polyethylene glycol) and argon + PEG. The molecular masses of PEGs differed from Mw 400 g mol(-1) up to Mw = 10000 gmol(-1) up to a pressure of 30.0 MPa at a constant temperature of 343 K. This technique was validated by conducting measurements of the interfacial tension between CO2 and pure water at a temperature of 318 K. The accuracy of the obtained results compared to the ones found in the literature was better than 4%. Additionally, the effect of temperature was also investigated by measuring the solubilities and the interfacial tensions in the systems CO2 + PEG 1500 and argon + PEG 1500 within the range of temperatures from 328 K up to 363 K. (C) 2015 Elsevier B.V. All rights reserved.