32 
Oil Spill identification - Round Robin 20045 
Drawing a horizontal line at the peak maximum of C15 (as added here 
to the figures) visualizes that C15 is not an outstanding maximum in 
source II (as it is in source I). 
As a result of the GC-FID analyses Sintef decided not to evaluate the 
GC-FID results further and to go directly to the GC-MS analysis, 
because all samples show the same type of oil and because the 
C17/pristane, C18/phytan and pristane/phytane ratios are weathered. 
Sintef discusses in their report the usefulness of the C17/pristane, 
C18/phytan and pristane/phytane ratios, which leads to the 
recommendation that those ratios should only be used carefully, 
because "generally the compounds in the C17 to C20 area are often 
affected by evaporative loss". 
The corresponding difference in the n-alkane distribution of source I 
and source II has clearly been found also by LVA (source II middle, 
source I below): 
Fig 9 
Gas Chromatograms (LVA) 
Based on the GC-FID analysis five of the nine labs have noticed that 
Source II shows differences compared to both spill samples. BMM 
decided, based on the GC-FID results, to eliminate Source II from the 
GC-MS analysis.