Fluorescence measurements coupled with cyclic linear sweep or potential-step modulation of the phase-boundary potential have been employed to distinguish the diffusion-limited transfer of protonated ofloxacin (OFX+) from the transfer accompanied by the interfacial adsorption at the water / 1,2dichloroethane interface of its Fe(III) complex [Fe(OFX)(2)](3+). In potential-step chronofluorometry in the presence of [Fe(OFX)(2)](3+) , an initial increase in fluorescence is followed by a decrease with potential and also with time for each potential pulse. This behavior is indicative of an adsorption process followed by rearrangement of the adsorbed complex, resulting in a compact layer with different optical properties. This accumulation of [Fe(OFX)(2)](3+), but not free OFX+, at the interface may have physiological significance in developing the function of OFX+ in biological systems.