The interfacial tension is a key quantity to phase and interphase behaviour of reservoir systems. Real systems consist of complex mixtures that are not easily accessible to theoretical considerations. By help of experimental analysis, main factors of influence can be determined that may be used for developing theoretical models and thus for obtaining deeper insight into dominating mechanisms. This work focuses on the role of carbon dioxide in gas and liquid mixtures comprising also hydrocarbons such as methane, n-pentane and n-heptane by determining the interfacial tension as a function of pressure in the range of 0.1-17 MPa at 313 and 323 K, gas composition and time. In the investigated systems, carbon dioxide shows to have a dominating effect caused by its high ability of dissolving in organic liquids and resulting in a strongly decreasing interfacial tension at elevated pressures. A further question addressed in the present work is in which way a changing concentration profile during mass transfer within a pendant drop is associated to the evolution of the interfacial tension. In binary systems, carbon dioxide is known to accumulate at the interface which happens immediately at its formation and covering any other dynamic effect. In ternary vapour-liquid-liquid systems that include water, mass transfer is shown to correlate with the time dependant interfacial tension. (c) 2012 Elsevier B.V. All rights reserved.