Knowledge about the distribution of surfactants between aq. and reverse micellar phases as well as the assocn. of surfactants with proteins are of major importance for assessing the practical feasibility of protein extn. by reverse micellar systems. The question of the fate of the surfactant has been addressed for the classical reverse micellar system based on brine/AOT/isooctane. For this purpose, AOT, (Aerosol OT, di-2-ethyl-1-hexyl sulfosuccinate) was synthesized in the presence of sulfite radioactively labeled with the isotope 35S. The synthesis of [35S]AOT as well as its use for tracer anal. with protein extn. are discussed. [on SciFinder (R)]