Electron impact GC/MS experiments were performed on a Finnigan TSQ700 triple quadrupole mass spectrometer Finnigan MAT, San Jose, CA) fitted with a Finnigan EI/CI ion source. The carrier gas was helium and the flow rate was kept at 1.1 ml/min throughout the run. The head pressure was maintained constant at 10 psi throughout the run. All the experiments were carried out in the splitless mode for about 1 min. The injector port and the interface were set at 250 and 260 degree Celcius, respectively. The oven temperature was programmed as follows: 75 degrees for 2 min then ramped at 25 deg C per min to 100 deg followed by 10 deg per min to 300 deg, hold for 5 min.

The instrument was used as a single quadrupole and scanned from 35 to 650 daltons for 0.65 second.