We describe the development and validation of an on-line solid-phase extraction of large-volume injections coupled to liquid chromatography-tandem mass spectrometry method for the simultaneous quantitation and confirmation of 14 selected trace organic contaminants in drinking and surface water. Selected compounds were: anti-infectives (clarithromycin, sulfamethoxazole and trimethoprim), an anticonvulsant (carbamazepine) and its transformation product 10,11-dihydrocarbamazepine, an antihypertensive (enalapril), antineoplastics (cyclophosphamide and methotrexate), herbicides (atrazine, cyanazine, and simazine) and two of their transformation products (deethylatrazine and deisopropylatrazine) and an antiseptic (triclocarban). The breakthrough volume determinations showed that out of all the investigated sorbents, the Strata-X on-line solid-phase extraction column showed the best performance. The method used a load volume of 10.0 mL and was validated using the corresponding matrices, yielding for most compounds, R(2)>0.99. Extraction recoveries ranged from 60 to 109%. The intra- and inter-day precision were <14 and <16%, respectively. The method detection limits ranged from 0.6 to 6 ng L(-1). Matrix effects were in general low. The performance of the on-line method was demonstrated with the analysis of real water samples. The application of alternative techniques of confirmation was also explored using accurate mass measurements on a time-of-flight mass spectrometer and the data-dependent reverse energy ramp scan on a triple quadrupole.