On Fig. 6, experimental values of retention time of methane (triangles) and ethane (squares) can be compared to the model (full lines),a good correlation was observed between experimental and calculated values, for both methane and ethane. To confirm these assumptions, mixture B was injected on an gas chromatograph hyphenated to a mass spectrometer (5977A Series GC/MSD System from Agilent Technologies, France) for oven temperature from 25◦C to 120◦C using a PLOT silica column (GS-GasPro60 mx0.320 mm, Agilent Technologies, France) with helium as carrier gas. The results showed a clear separation between the air (assumed to be a hold-up time marker) and methane in the range 25◦C–70◦C. Above 70◦C, methane appeared co-eluted with air and the two peaks were not distinguishable meaning that methane retention was negligible above 70◦C.