A straight forward and non-invasive strategy to quantify vapour-liquid equilibria (VLE) of the ternary system acetone, water and carbon dioxide (CO2) is reported. The strategy is based on extracting the composition of a ternary mixture from its Raman spectrum. An isolated Raman signal of acetone, which is not interfered with Raman signals of water or CO2, is used as a reference signal. The capability of the strategy introduced is demonstrated by the agreement with VLE data obtained by the other authors that used conventional methods at elevated pressures up to 10 MPa and temperatures up to 353 K. The advantages of the introduced method are its non-invasive sampling method, its insensitivity to misalignment or distortions of the excitation and signal paths as well as power fluctuations of the excitation beam, its fast accessibility to the mixture composition and the general transferability to all systems whose Raman spectrum shows a spectrally isolated strong Raman signal which can be assigned to one specific compound. (C) 2013 Elsevier B.V. All rights reserved.