A solid-phase extraction (SPE) procedure with the use of superparamagnetic Fe(3)O(4) nanoparticles as extracting agent was developed for HPLC-ESI-MS/MS analysis. Four most heavily used triazine pesticides (herbicides) were taken as the test compounds. The NPs showed an excellent capability to retain the compounds tested, and a quantitative extraction was achieved within 10min under the testing conditions, i.e. 100 microL NP solution was added to 400 mL sample in a beaker with stirring. After extraction, the superparamagnetic NPs were easily collected by using an external magnet. Very importantly, analytes retained on the Fe(3)O(4) NPs could be quantitatively recovered by dissolving the NPs with an HCl solution, allowing subsequent HPLC-ESI-MS/MS quantification. A capillary HPLC-ESI-MS/MS method with the present NP-based SPE procedure was developed for the determination of triazines including atrazine, prometryn, terbutryn, and propazine. Atrazine-d(5) was used as internal standard. The method had an LOD of 10 pg/mL atrazine, and a linear calibration curve over a range from 30 pg to 50.0 ng/mL. Simultaneous determination of the four triazine pesticides in water samples taken from local lakes was demonstrated.