The study of adsorption of squalene onto two fumed silica samples submitted to a controlled trimethylsilylation process was made using inverse liquid chromatographic frontal analysis in anhydrous heptane. Their monolayer capacities of adsorption, Langmuir's and Henry's constants were determined from the desorption isotherms, it was observed for fumed silica having a specific surface area of 130 m(2)/g that they show sudden change for two critical trimethylsilyl coverage ratio around 25 % and 50 %. This evolution abeys to a simple model based on a simple random repartition of the TMS groups and corresponds to surface transitions due to the presence of the TMS groups on the silica surface as previously evidenced by IGC analysis, rheological measurements or wettability studies. But, this model fails in the cas of a fumed silica exhibiting a higher specific area equal to 300 m(2)/g. These difference in behaviours between these two silica could be attributed to the surface roughness.