A solid phase microextraction (SPME) device (Supelco Inc., Bellefonte, PA, USA) containing a fused-silica fiber (75 lm length) coated with a 50/30 lm layer of Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS) was used. The vial was allowed to stand at 40 C for 15 min to equilibrate its headspace.