GC-MS analysis was performed using an Agilent Technologies (Santa Clara,CA)7890A gas chromatograph and an Agilent 7683B anto injector coupled with a 5975C VL Agilent mass selective detector.
The mass spectral scan rate was 2.86 scans/s.
The Gc was operated in splitess mode with a helium (grade 5) flow rate of 0.7 ml/min and the column head pressure was 10 psi.
The MS was operated in the electron impact (EI) mode using an ionization voltage of 70 eV and a source temperature of 230 c.