Why 



Gas Chromatography 



Gas chromatography is an analytical tool 

 used to analyze petroleum hydrocarbons. This 

 technique separates the various constituent 

 hydrocarbon compounds according to the size 

 and structure of their molecules. The oil which 

 is in a sample, such as sediment or tissue, is 

 extracted with a solvent that isolates the 

 hydrocarbons. Each component or fraction of 

 these hydrocarbons can then be separated and 

 measured. As different fractions emerge from 

 the separation process, a recorder graphs the 

 amounts of hydrocarbon, forming a pattern or 

 chromatogram. This chromatogram is a sort of 

 "fingerprint" which identifies and distinguishes 

 between different types of oil. 



Sp 



Trace 

 illed Oil? 



Reports from the West Falmouth 

 area suggested that everything was 

 back to normal shortly after the 

 cleanup operations were terminated. 

 Bathers were enjoying the water, and 

 the beaches were as beautiful as 

 ever. These reports were misleading. 

 When spilled oil can no longer be 

 seen, it does not mean that the oil, at 

 toxic levels, is not present. Oil can be 

 lethal or have significant sublethal ef- 

 fects in very small concentrations, 

 concentrations as low as several parts 

 per billion. 



Sensitive analytical techniques can 

 detect these very small, but impor- 

 tant, concentrations of oil. The 

 techniques of analytical chemistry can 

 also differentiate between hydro- 

 carbons from petroleum and the 

 naturally occurring or biogenic hydro- 

 carbons that are present in all living 

 things. One analytical technique, gas 

 chromatography, can even distinguish 

 between different types of oil. 

 Analytical chemistry provides the 

 tools used to trace oil as it disperses 

 into the environment, to monitor 

 changes in the oil that occur as a 

 result of weathering, and to relate 

 this information to biological surveys 

 and studies of organisms. 



150 200 250 



Temperature (C°) 



100 150 ^uu ^ou 300 100 



Temperature (°C) 



Gas chromatogram "fingerprint" of fresh No. 5 fuel oil (A) and the same oil after weathering for 41/2 months (B). 



300 



Source: Cretney. W.J. et al.,1978. Long Term 

 Fate of Heavy Fuel Oil in a Spill- 

 Contaminated B.C. Coastal Bay. Journal of 

 Fisheries Research Board of Canada. 35, (5). 



11 



