Carrier gas was ฮีเลียม (1 ml/min) and the chromatographic conditions were as follows: initial oven temperature was maintained at 40C for 10 min, and subsequently programmed from 40 to 120C at a rate of 3C/min and at a rate of 10C/min from 120 to 250C where it was held for another 5 min. Injector Ta: 250C; Mass range: 30±350 amu; Solvent delay: 4 min.; electron impact at 70 eV.