SPME extraction was performed with carboxen–polidimetilsiloxano
(CAR–PDMS) fibre. The fibre was conditioned at
300 C for 1 h prior to use. Blank desorptions were periodically carried
out. Samples (20 mL) were transferred into vials (40 mL, Supelco)
which contained 20% (w/v) sodium chloride salt, 150 lL
sodium hydroxide 6 mol L1. Internal standard at 50 and 25 lg L1
of, respectively, dichloromethane and diiodomethane were used.
The incubation and extraction temperature was 30 C. The samples
were equilibrated for 8 min before the extraction step. The
speed of the magnetic stirring was 1000 rpm. The fibre was immersed
in the headspace of the sample for 15 min, immediately
drawn back into the needle and transferred without delay (less
than 5 s) into the injection port of the GC. A desorption time of
3 min at 280 C was used in this study. All analysis was performed
in triplicate.