24 
Fig. 19: Mass-chromatograms of mass 192 (M-phenanthrenes, M-anthracene) of FIFOs (same 
samples as in Fig. 15). 
Fig. 20: Mass-chromatograms of mass 234 (tetra-M-phenanthrenes, M- benzo-naphtho- 
thiophenes) of HFOs (same samples as in Fig. 15). 
Figures 19 and 20 show that the characteristic clusters of aromatics from cracking residues 
can be used for an unequivocal identification of HFOs in cases where aromatics are not 
readily discernible by GC screening (Figure 15 samples on the right side). 
Thus, despite the highly different composition of the HFOs shown in Figures 14 and 15 and 
their different aromatic contents, these 8 oils are hardly discernible by their aromatic clusters. 
The ratio of 2-M-phenanthrene to 1-M-phenanthrene, for example, expressed as 100 *(2-M- 
phen/(2M-phen+lM-phen)) of these 8 samples is 66 +- (max.) 1%.