Enantiomeric Composition of Chiral Polychlorinated Biphenyl Atropisomers in Aquatic and Riparian Biota

Abstract

The enantiomeric composition of polychlorinated biphenyl (PCB) atropisomers was measured in river and riparian biota (fish, bivalves, crayfish, water snakes, barn swallows) from selected sites throughout the United States by using chiral gas chromatography/mass spectrometry. Nonracemic enantiomeric fractions (EFs) were observed for PCBs 91, 95, 136, and 149 for aquatic and riparian biota from Lake Hartwell, SC, a reservoir heavily contaminated with PCBs, and for these congeners and PCBs 132, 174, 176, and 183 in river fish and bivalves nationwide. Fish and bivalves showed marked differences in EFs as compared to sedimentfound atthe same sampling sites, thus suggesting that PCBs are bioprocessed in biota in a different manner from those found in sediment (e.g., reductive dechlorination). Species-dependent patterns in PCB EFs were observed, which suggest differences in the ability of different species to bioprocess PCBs enantioselectively, most likely by metabolism. The presence of nonracemic PCBs in fish and bivalves suggests greater metabolic degradation of PCBs in these organisms than indicated from previous achiral studies and underscores the powerful potential of chiral analysis as a tracer of environmental bioprocesses.

Chirality as an Environmental Forensics Tool

“…This observation suggests the possibility of in vivo enantioselective processing of a-HCH by this species [137]. Likewise, other studies have found nonracemic amounts of a-HCH [111], PCBs [66,196], a-HBCDD [193], and the musks HHCB, AHTN, ATII, and AHDI [197] in several species of bivalves: blue mussel, Mytilus edulis; the freshwater clam, Corbicula sp. ; the clams Mya truncate and Serripes groenlandica; and zebra mussel, Dreissena polymorpha, respectively.…”

“…Nonracemic PCBs were observed in livers of sharks [87,222] and groupers [87], while Arctic cod in the Northwater Polynya had racemic PCBs [192]. Similar nonracemity in PCBs was also observed for a number of freshwater fish species in the highly contaminated Lake Hartwell reservoir, as well as in streams and rivers throughout the US [196].…”

Distribution of Chiral PCBs in Selected Tissues in the Laboratory Rat

“…The column found to provide the best separation of atropisomers for the most chiral PCB congeners was a ChiralsilDex column (Chrompack, Raritan, NJ, USA), 25 m × 0.25 mm id × 0.25 μm film thickness, with an immobilized chiral phase of permethyl 2,3,6-tri-O-methyl β-cyclodextrin on a polysiloxane backbone stationary phase. A G-TA column (Astec, Whippany, NJ, USA), a B-PA column (Astec), and a BGB172 column (BGB Analytik AG, Anwil, Switzerland) were also explored in an attempt to separate additional chiral PCB congeners present in the tissues (18), but proved to be less proficient than the Chiralsil-Dex column.…”

Chiral separation of polychlorinated biphenyls using a combination of hydroxypropyl-γ-cyclodextrin and a polymeric chiral surfactant

“…Chiral PCBs if present in technical formulations is usually released as racemic mixtures. However, nonracemic enantiomeric ratio on various samples suggests different metabolic pathways for the biological processing of PCB enantiomers [2][3][4][5]. In addition, enantiomers of some chiral PCBs (PCB 88, 139 and 197) have been shown to possess different biological activity [6,7].…”