38 
%32abS 
Fig. 31: %32abS of 260 crude oil samples (x-axis: sample number) 
%32abS thus cannot be used for result verification in Oil Spill Identification because this 
parameter must be regarded as a constant here. There is definitely no reason to determine a 
constant. 
A Since oil spill identification means in fact oil discrimination, those compounds or 
compound ratios should preferably be used for result verification, which show the 
biggest differences between oils. Although these may vary from case to case, 
some of them can be regarded as “key”-parameters, which require special 
consideration. 
When we move from all oils to a distinct production area, additional parameters may become 
less and other parameters may become more important. 
The rare 25-norhopane, for example, is found in a small amount in crude oil from the central 
platform of the Norwegian Oseberg field (about 7 % in relation to hopane), whereas this 
compound is near the detection limit in samples from other platforms of this area (about 1 % 
in relation to hopane). If this parameter is handled in the same way as all other parameters, 
only a small difference is demonstrated (Figure 32). This difference is about the same as the 
difference in the amount of 28-bisnorhopane (peak on the left of 25-norhopane).