represents the retention factor of C2 for both N2 and CO2 normalized to the retention factor of C2 using helium at the same temperature. Whatever the oven temperature, kC2 decreased when nitrogen or carbon dioxide pressure increased. Such kind of behavior is known for adsorption chromatography [4,14–22], the molecules of the carrier gas being adsorbed on the stationary phase surface reducing the number of available adsorption site accessible for the analyte leading to a decrease of retention factor (Eq. (7)). The effect of the carrier gas is less significant when temperature increased or when carrier gas pressure decreased, due to lower adsorption of carrier gas molecules.