Gas chromatography - mass spectrometry (GC-MS) analysis was performed on an Agilent 6890 GC equipped with 5973 N mass selective detector and an HP-5 (5% phynylmethylpolysiloxane) capillary column. The oven temperature was programmed from 50 to 280 °C at the rate of 4 /min and held at this temperature for 5 min. The inlet and interface temperatures were 250 and 280 °C, respectively. The carrier gas was helium at a flow rate of 1.0 mL/min (constant flow). The sample (0.2μL) was injected with a split of 20:1. Electron impact mass spectrometry was carried at 70 eV. Ion source and quadrupole temperatures were maintained at 230 and 150 °C respectively.