Abstract: An appropriate amount of cut and crushed printed circuit board (PCB) sample was taken and extracted with HCOOH-CH3OH(0.1+99.9) mixture ultrasonically. The extract was evaporated to ca. 1 mL in a rotary evaporator at 45 ℃, 5 mL of H2O was added and the pH value of the solution was adjusted to 4-5 with dil. formic acid and dil. aq. ammonia. The solution was then purified by passing through the Oasis WAX SPE micro column and eluting with mixture of NH3(aq.)+CH3OH(2+98). The eluate was blown with N2 to near-dryness, and made up its volume to 1 mL with the mobile phase solution mentioned below. An aliquot of 5 μL of the sample was introduced for analysis. The Acquity UPLC BEH C18 column with column temp. of 30 ℃ was used for chromatographic separation, using a mixture of 5 mmol·L-1 NH4OAc solution and acetonitrile(60+40) as mobile phase for elution (flow-rate: 0.3 mL·min-1). ESI with negative ionization mode and scanning mode of MRM were used in the MS/MS analysis. Linearity range for perfluoro-octane sulfonate was found between 1.0-1 000 μg·kg-1. Lower limit of determination (10S/N) was found to be 1.0 μg·kg-1. Values of recovery found by standard addition method were in the range of 89.9%-99.3%.