The purpose of the paper is to present the result of combined application of anionic collectors such as sodium N-dodecanoyl sarcosine and sodium dodecanate, both of which are improved by use of cationic additional reagents, e,g. alkylammonium chloride, as co-collectors within the flotation of fluorite. The use of sodium N-dodecanoyl sarcosine in combination with dodecylammonium chloride shows synergistic effect in flotation efficiency, Moreover, adsorption of the anionic collector at the liquid/air interface is influenced by cationic surfactants as could be demonstrated by investigations of Langmuir films at the air-water interface. Amine incorporation in floating sarcosine monofilms has a great stabilization effect and the final amine content in the mixed film is related to the maximum in flotation recovery.