The study of Titan's photochemical haze is thus a precious tool to gain knowledge on the primitive atmosphere of Earth. The simulation in the laboratory of analogs of this haze has proved itself to be a useful tool to improve our knowledge of the aerosols formation on Titan. Tholins (analogues of aerosols) produced by PAMPRE experiment were found to be mostly insoluble, with only a third of the bulk sample that can be solubilized in methanol [1]. This partial solubility limited the previous studies by mass spectrometry, which were done only on the soluble fraction. In this work, we compared both soluble and insoluble fraction of tholins in methanol using an ultra-high resolution mass spectrometer equipped with a Laser desorption ionization (LDI) source, to get full insights on these complex samples. Major differences are observed in the molecular composition of the soluble and the insoluble fraction [2].