20/11/1998 · A Shimadzu QP5000 gas chromatograph–mass spectrometer (Kyoto, Japan) with electron-impact ionization detector was used. The gas chromatograph was set up as follows: a DB-1 capillary column (60 m×0.25 mm, film thickness 0.25 μm, J&W Scientific, Folsom, CA, USA), column temperature, 70°C; injector and interface temperatures, 200°C and 250°C; carrier gas (helium) flow-rate, 1.7 ml/min