Enantioselective gas chromatography with electron
capture negative ion mass spectrometry (GC/ECNI-MS)
was employed to investigate the fate of toxaphene residues
in contaminated sediment (source) and biota (receptor)
representing several levels of an aquatic food web. Samples
were collected from an estuarine marsh that was impacted
by discharge from a former toxaphene plant. Several
penta- to nonachlorobornanes were identified and
enantiomerically resolved on a chiral stationary phase.
Additional peak confirmation was obtained after fine
fractionation of extracts on silica. Previously identified
congeners including B6-923 (Hx-Sed), B7-515 (P-32),
B7-1001 (Hp-Sed), B8-806/9 (P-42), B8-1412, B8-1413
(P-26), B8-2229 (P-44), B9-1679 (P-50), and B9-2206 (P-63)
were detected, as were several unknown penta- and
heptachlorobornanes. The majority of prominent congeners
were essentially racemic in marsh sediment (maximum
deviation 15%). In contrast, several congeners as well as
several unknown hepta-CTTs were enantioselectively
depleted in lower food web organisms; the enantiomer
ratios (ERs) for B6-923 and B7-1001 in small fish (Fundulus
sp.) were ∼2 and 0.6, respectively. These significant
alterations of the ERs prove that even low-trophic level
biota is able to degrade toxaphene components to some
degree. In higher level predators, the ERs for B7-1001 were
closer to racemic. Irrespective of trophic level, little or
no shift in the ERs for B8-1413 (P-26) and B9-1679 (P-50),
two recalcitrant chlorobornanes in mammals, relative
to sediment were observed. These results indicate that
biochemical transformations within the scope of the estuarine
food web studied likely act to alter the residue pattern
and the ultimate fate of toxaphene.