M8 PM Chiral Chemistry: Toxicology of Environmental Contaminants and Phase Transfer
Monday, 14 November 2005: 1:50 PM - 5:30 PM in 337-338

(HAL-1117-739666) Changes in enantiomeric fractions of PCB atropisomers in composted soil using three modified cyclodextrin modified capillary columns.

Hall, April¹, Lee, Cindy¹, ¹ Clemson University, Anderson, SC, United States

ABSTRACT- Chiral analysis of four congeners of polychlorinated biphenyls (PCBs) were conducted on soil from treatability studies performed at the Department of Energy Savannah River Site (SRS) in an attempt to bioremediate PCBs and chlorinated pesticides such as DDT in the Chemical, Metal, and Pesticide (CMP) pits via composting. Microcosm studies were conducted under aerobic and anaerobic conditions to determine the effectiveness of composting. Achiral analysis of PCBs showed the disappearance of higher chlorinated congeners and the subsequent appearance of dichlorobiphenyls, possibly indicating reductive dechlorination in anaerobic microcosms treated with reduced anaerobic minimal medium (RAMM) and molasses. Aerobic studies showed removal of lower chlorinated congeners such as the tri- and dichlorobiphenyls. However, due to the low concentration (2 ppm) of PCBs present in the soil, the changes are not statistically significant. Chiral analysis provided more conclusive evidence that bioremediation has occurred by changes in enantiomeric fractions (EFs). PCB 84, PCB 91, PCB 95, and PCB 149 were identified using a Chirasil-Dex capillary column coupled to a HP6890 equipped with an electron capture detector (ECD). Chiral analysis of the initial compost samples indicated that bioprocessing occurred prior to the microcosm study by the deviation of the EF from 0.5, indicating that the mixture is no longer racemic. After incubation, very small, but meaningful evidence of enantioselective bioprocessing was documented. In several of the microcosms, chiral analysis of PCB 149 shows that reversed enantioselectivity occurred during aerobic and anaerobic treatments. For all four chiral congeners quantified, changes in EF were observed in killed controls. In order to confirm these data, two other chiral columns, B-DM Chiraldex and Cyclosil-B will be implemented. These columns will also allow quantification of other chiral congeners that were not quantifiable by the Chirasil-Dex column. Differences in data from each of the columns will be discussed.

Key words: chiral chromatography, PCBs, biodegradation, reductive dechlorination