I'r - Memorial University of Newfoundland

It was shown that the right choice ofsolvent andsediment to solvent ratio are
important for favorable recovery results (Farrington and Tripp, 1975; Grimalt el 01., 1984;
Ehrhardt er at.; 1991) . The increased polarity ofsolvent usually resuJts in more
exhaustive recoveries. Therefore, the polarity ofsolvent was increased as compared to
that used by O 'Mallcy(I994). The latter was achieved by adding 10% ofmethanol to the
pure dichlorometbane employed in the previous study. In addition, the amount ofsolvent
was doubled as increased sample weights (17-]Og) were utilized. This allowed the
appropriate sediment.so lvent ratio to be maintained at a level similar to that reported by
O·Malley (I994).
The previously prepared samples were placed in precleaned cellulose thimbles and
Soxhlet extracted using ]00 mI ofsolvent in a darkened fwnehood. The extraction time
was 24 hours with a rate of ] cycles per hour. The extracts were further concentrated to
1-2 ml using a rotary evaporator at 3SoC then dried to constant weight under a stream of
nitrogen. Samples were stored in a freezer prior to the following class separation
procedure.
Class separation: This procedure invo lves separation ofthe fraction that contains
PAH from the total extracts (Fig. 3.1.2). Silica column chromatography has been found
to provide satisfactory separation ofPAH (e.g., Youngblood andBlumer, 1975; Giger and
Schaffner. 1978). However. it was shown that certain modifications can further improve
the results ofpurification (O 'Malley, 1994; Stark, 1997). A higher degree ofbydrocarbon
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