A magnetic material based on N-methylimidazolium ionic liquid and Fe(3)O(4) magnetic nanoparticles incorporated in a silica matrix has been used to extract and preconcentrate sulfonylurea herbicides, such as thifensulfuron methyl (TSM), metsulfuron methyl (MSM), triasulfuron (TS), tribenuron methyl (TBM) and primisulfuron methyl (PSM) from polluted water samples, prior to their analysis by capillary liquid chromatography with a diode array detector (DAD). Under the optimum conditions, this method allows the determination of TSM, MSM, TS, TBM and PSM in a linear range between 5 and 100 ng mL(-1), with relative standard deviation values lower than 5.3% (n = 10), in all cases. Detection limits ranging between 1.13 and 2.95 ng mL(-1) were achieved. The usefulness of the proposed method was demonstrated by the analysis of river water samples, obtaining recoveries higher than 91%.