An instrumental set up including on-line solid-phase extraction, nano-liquid chromatography, and nanospray mass spectrometry is constructed to improve the sensitivity for quantitation of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in surface water. Sample volumes of 1000 microL are loaded onto a microbore 1.0-mm i.d. x 5 mm, 5 microm Kromasil C(18) enrichment column by a carrier solution consisting of 10mM ammonium acetate in acetonitrile-water (10:90, v/v) at a flow rate of 250 microL/min, providing on-line analyte enrichment and sample clean-up. Backflushed elution onto a 0.1-mm i.d. x 150 mm, 3.5 microm Kromasil C(18) analytical column is conducted using an acetonitrile-10mM ammonium acetate solvent gradient from 30% to 70% acetonitrile. Water samples are added with internal standard (perfluoroheptanoic acid) and filtrated prior to injection. The mass limits of detection of PFOA and PFOS are 0.5 and 1 pg, respectively, corresponding to concentration limits of detection of 500 pg/L and 1 ng/L, respectively. The total time spent on sample preparation, chromatography, and detection is approximately 12 min per sample. The method was employed for the determination of PFOS and PFOA in urban river water.