16 
Fig. 8: Gas-chromatograms of different lubricating oils. 
2.2.1.2 GC-MS analysis 
Lubricating oils have been found to be rich in biomarker compounds. But depending on the 
boiling range covered, different biomarkers are present in different proportions. Thus, the 
relation of compounds (or compound ratios) is significantly influenced by the boiling cut of 
the particular lubricating oil concerned (Fig. 9). 
Fig. 9: Hopanes (mass fragment 191) of different lubricating oils (same oils as in Fig. 8).