The invention relates to a method for obtaining porous hollow fibers having molecularly imprinted spheres embedded therein, said method comprising the steps of: simultaneously and independently injecting a doping solution and a pore-forming solution into an extrusion die extruding or spinning porous hollow fibers coagulating the porous hollow fibers that leave step (b) in an aqueous solution with an aqueous solution having a temperature between 15° C.-25° C. winding the flexible porous hollow fibers coagulated in step (c) leaving them to dry and storing same under vacuum conditions. The resulting porous hollow fibers are used to form filtrating modules in which a plurality of fibers are disposed longitudinally and in parallel. The filtrating modules can be assembled together to form filtering devices intended, in a preferred example, for gradual blood purification and the subsequent qualitative and/or quantitative identification of the molecules retained in the first filter of each filtering module. The invention also relates to the operating method of the filtering device.
