The GC was programmed at 60°C for 4 min and then increased at 10 C/min to 280 C, and finally held with an isothermal for 5 min. The injector temperature was 250°C, and the injection size was l Hl. The flow rate of the carrier gas (helium) was 1 ml/min. The ion source temperature was 230°C for the mass selective detector. The compounds were identified by comparison with the NIST Mass Spectral Database [11].