Analysis of polycyclic aromatic hydrocarbons formed during off-line pyrolysis of ergosterol by GC-MS-SIM

The formation of polycyclic aromatic hydrocarbons (PAHs) during pyrolysis of ergosterol at 700 and 900 C is investigated. The pyrolysis is carried out in a furnace-type pyrolyzer with an off-line mode, and the formed PAHs are trapped by a hollow fused silica capillary (0.7-m length, 0.53-mm i.d.), and the capillary is immersed in liquid nitrogen during pyrolysis and trap periods. The trapped organic products (including PAHs) in the capillary are eluted with dichloromethane. The qualitatively and quantitatively analysis of PAHs is carried out by gas chromatography-mass spectrometry with selective ion monitoring mode. It is found that the off-line pyrolysis apparatus has some advantages including less secondary reactions and better reproducibility. The results show that the yield of most PAHs increase with temperature, the increase is particularly large for two- and three-ring PAHs. The pyrolysis of ergosterol shows that the native cyclic ring structure leads to the formation of PAHs.