Application of stir bar sorptive extraction to the determination of polycyclic aromatic hydrocarbons in aqueous samples

The technique of stir bar sorptive extraction is used for the determination of polycyclic aromatic hydrocarbons (PAH) in aqueous samples. The PAHs are extracted with 10-mm stir bars (Gerstel Twister) coated with 0.5 mm polydimethylsiloxane and analyzed with a gas chromatography–mass spectrometry system. The influence of methanol and hyamine addition to the samples for preventing wall effects is investigated at 100 ng/l. The results indicate improved sensitivity using hyamine addition to the samples. The optimal extraction time was found to be between 3 and 4 h. The reproducibility of the method, as determined by nine replicate measurements, is between 5 and 15% at 10 ng/l and between 3 and 9% at 50 ng/l. Carry-over, which was evaluated at 500 ng/l by desorbing the same Twister three times, seems to be negligible for most of the compounds. In worst cases, carry-over of up to 7% was found for indeno[1,2,3]pyrene, dibenz[a,h]anthracene, and benzo[g,h,i]perylene. The technique shows excellent linearities for 5 point calibrations. Detection limits are between 0.1 and 2 ng/l.