Neutron reflectivity on liquid/liquid (LL) interface will be performed to study the distribution of gadolinium cation across the interface. The chosen system will allow to compare two types of incident geometries that can be tested on Figaro. There are also two objectives: a first one that will allow to compare data with previous experiments but using another type of cation in the lanthanide series (Nd has been already studied with a different separation factor). The second is to prepare a future experiment that will allow to couple reflectivity and gamma fluorescence detection to better characterize the cation distribution at the LL interface using only neutrons.