Soxhlet extraction, homogenization with Na2So4 in a Virtis homogenizer, and KOH-methanol digestion methods of extracting hydrocarbons from marine organisms have been tested and compared using subsamples of a clam (Marcenaria mercenaria) homogenate. The amounts of hydrocarbons were determined gravimetrically and the composition was partially characterized by gas chromatography. There was a statistically significant difference between the results of the Virtis vs. Soxhlet and Soxhlet vs. digestion methods. However, in practice the difference is small and would be apparent only if large numbers of replicate measurements were made.
The concentration of hydrocarbons in clams from three locations, a polluted harbor area, a less polluted bay area, and a relatively clean bay have been determined. The composition was partially characterized by gas chromatography.
Subsamples of clam homogenate spiked with 10 ppm API No. 2 fuel oil have been analyzed. Only 5 to 6 ppm of the spike were detected. Gas chromatographic analysis indicated that the lower molecular weight components of the spike were lost. The gas chromatographic passive tagging parameters were altered from those of the API No. 2 fuel oil by interference from hydrocarbons already present in the clams prior to spiking.