The use of three separation modes (normal and reversed-phase adsorption chromatography and gel chromatography) with an ultraviolet absorption detector of variable wavelength provides the basis for a very sensitive method for the determination of phthalate esters in river water. Phthalates in river water were extracted with n-hexane and the extract was injected into three chromatographic systems [porous polymer beads-n-hexane (at 224 nm); porous polymer beads-methanol (at 224 nm); and polystyrene GPC gel-chloroform (at 243 nm)] without any pre-treatment such as clean-up concentration. Average concentrations of approximately 45 ppb of di-n-butyl phthalate (DBP) and 10 ppb of di-2-ethylhexyl phthalate (DOP) were found in a given river water. Phthalate concentrations as low as 2 ppb could be determined. The limit of determination could be lowered by the use of concentration process. The absolute detection limit was 2 ng of DOP at 224 nm.