M8 PM Chiral Chemistry: Toxicology of Environmental Contaminants and Phase Transfer|
Monday, 14 November 2005: 1:50 PM - 5:30 PM in 337-338
160 (WON-1117-844706) Enantiomeric composition of chiral pharmaceuticals in natural waters and wastewaters.
Start time: 1:50 PM
Wong, Charles1, Nikolai, Lisa1, MacLeod, Sherri1, McClure, Evelyn1, 1 University of Alberta, Edmonton, AB, Canada
The occurrence and flux of stereoisomers of commonly used pharmaceuticals were determined in surface waters and wastewaters of the North Saskatchewan River and at Lac la Biche, Alberta, in order to understand the enantiomer composition of such chiral drugs in the aquatic environment. Chiral analysis has been extensively used in recent years to detect and gain insight into biologically-mediated processes affecting environmental pollutants. However, most of the work done to date has focused on legacy POPs (e.g., PCBs and organochlorine pesticides). Less emphasis has been placed on the plethora of current-use chemicals of emerging concern that are optically active, including pharmaceuticals. Surface water, wastewater, and sewage treatment plant effluent from a large city (North Saskatchewan River at Edmonton) and smaller population site (Lac la Biche) were extracted for target compounds using solid phase extraction, followed by chiral HPLC/MS/MS analysis under both positive (e.g., fluoxetine, paroxetine, omeprazole, temazepam) and negative (ibuprofen, ketoprofen, fenoprofen, metoprolol, propanolol) electrospray ionization. Enantiomer resolution ranged from 0.8 to 3.0 on a suite of chiral HPLC stationary phases (e.g., Chiralpak AD-RH, Chirobiotic V, Whelk-O 1). Achiral targets (e.g., clofibric acid, diclofenac, carbamazepine) were resolved from achiral targets, allowing for stereochemical information to be obtained at the same time as achiral quantitation. Detection limits were in the ng/L range, comparable to achiral HPLC/MS/MS analysis. Enantiomer fractions of target analytes were nonracemic and varied among surface waters and wastewaters, showing that insights on biological weathering of pollutants gained from legacy POPs are applicable to current-use chiral pharmaceuticals.
161 (MAT-1117-740527) Movement of Bioavailable Contaminants from ex planta to in planta Regions of the Soil/Plant System: Differences among Cucurbitaceae Cultivars.
Start time: 2:10 PM
Mattina, MJ1, Eitzer, B1, Iannucci-Berger, W1, Isleyen, M1, White, J2, 1 Department of Analytical Chemistry, CT Agricultural Experiment Station, New Haven, CT, USA2 Department of Soil&Water, CT Agricultural Experiment Station, New Haven, CT, USA
Data from field and greenhouse studies conducted in the past have established the exceptional ability of plants of the Cucurbitaceae family to uptake soil-sequestered pollutants. In the present set of experiments three representative Cucurbitaceae, Cucurbita pepo spp. pepo (cv. ′Black Beauty′), Cucurbita pepo spp. ovifera (cv. ′Zephyr′), and Cucumis sativis (cv. ′Marketmore′) were grown in rhizotrons containing soil contaminated with highly weathered technical chlordane, dichloro–diphenyl–ethanes and –ethenes, and polyaromatic hydrocarbons. Movement of the contaminants through the soil/plant system was studied by comparing contaminant concentration in the bulk soil, soil pore water, whole root tissue, xylem sap, and whole aerial tissue. Techniques were developed for collecting rhizosphere soil pore water and analyzing it to determine concentrations of organic pollutants. This permitted calculation of bioconcentration factors (BCFs) based on concentration of the analyte of interest in the xylem sap versus that in the pore water. The bioconcentration factors so determined for the sum of five chlordane residues (two enantiomers of trans-chlordane, TC; two enantiomers of cis-chlordane, CC; and achiral trans-nonachlor, TN) were 36, 40, and 23 for ′Black Beauty′, ′Zephyr′, and ′Marketmore′ respectively. Furthermore, there was consistent enantioselectivity based on cultivar noted for some of the chiral chlordane components. For the sum of dichloro–diphenyl–ethanes and –ethenes the comparable BCF values were 19, 4, and 0.8. Fluxes in ng/hr/root mass for chiral and achiral contaminants also showed consistent differences among cultivars. Thus, passage from the ex planta to the in planta regions of the soil/plant system is dependent on both the organic pollutant and the cultivar. Empirical data from this set of rhizotron experiments provide insight into mechanisms of movement of highly hydrophobic organic contaminants from ex planta to in planta portions of the soil/plant system
162 (EIT-1117-219445) Uptake of chiral and achiral chlordane components by ecotypes of Arabidopsis thaliana .
Start time: 2:30 PM
Eitzer, B1, Mattina, M.J.1, Iannucci-Berger, W.1, 1 The Connecticut Agricultural Experiment Station
The use of plants to remediate soil contaminated with organic compounds has long been a goal. However, it has been predicted that many organic chemicals have sufficiently large Kow (log Kow>3) that uptake by plants should be precluded. In studies over the past several years our laboratory has found that some species of plants, such as Cucurbitacea have a unique ability to uptake organic chemicals from soil despite the fact that these chemicals have large Kow's. We are now trying to understand the mechanisms that control this uptake. The genomics of Arabidopsis thaliana has been well characterized. Studies of uptake by Arabidopsis thaliana could therefore lead to insights in genomic characteristics controlling uptake, which in-turn could lead to improved plants for phytoremediation. Chiral gas chromatography/ion trap mass spectrometry is used to determine the concentration of chiral and achiral components of chlordane in the soil and vegetation growing in that soil. Tracking of chiral components leads to insight on the movement of these chemicals. Bioaccumulation by Arabidopsis thaliana will be reported and compared to the uptake of these same components by Cucurbitacea.
163 (HAL-1117-739666) Changes in enantiomeric fractions of PCB atropisomers in composted soil using three modified cyclodextrin modified capillary columns.
Start time: 2:50 PM
Hall, April1, Lee, Cindy1, 1 Clemson University, Anderson, SC, United States
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.
(58137) COFFEE BREAK.
Start time: 3:10 PM
164 (QIN-1117-749913) Difference of Pyrethroid Enantiomers in Their Degradation in Soils.
Start time: 3:50 PM
Qin, S1, Gan, J1, 1 UC, Riverside, Riverside, CA, USA
Synthetic pyrethroids contain two or three chiral centers, making them a family of pesticides with the highest number of enantiomers. Our recent studies showed significant differences in aquatic toxicity between the stereoisomers of the same compound. To better understand the ecotoxicological effect and fate of synthetic pyrethroids, chirality in biodegradation of pyrethroid compounds should be also considered. In this study, enantiomers of cis-bifenthrin were isolated on chiral HPLC and the enantiopure isomers were examined individually for their degradation rates in a soil and a sediment at 20°C under either aerobic or anaerobic conditions. The study results show that R-cis-bifenthrin degraded faster than S-cis-bifenthrin under aerobic conditions in both soils. However, under anaerobic condition, S-cis-bifenthrin was found to have a faster degradation rate. Isomer conversion did not occur during degradation in soil. As only biological interactions can be chiral selective, the enantioselectivity observed in degradation of cis-bifenthrin should be a result of different microbial communities under different test conditions. Enantiomers of two other pyrethroids, permethrin and cypermethrin, were also isolated and studied under similar conditions, and the role of microorganisms was further ascertained by including sterilization treatments. These results and their implications will be discussed.
165 (KON-1117-829754) Investigating the enantioselective toxicity of conazole fungicides in rainbow trout through NMR-based metabolomics.
Start time: 4:10 PM
Konwick, B1, Fisk, A1, Garrison, W2, Kenneke, J2, Ekman, D2, 1 University of Georgia, Athens, GA, USA2 U.S. Environmental Protection Agency, Athens, GA, USA
The conazole fungicides represent a large group of compounds widely used agriculturally for the protection of crops and pharmaceutically in the treatment of topical and systemic infections. Almost all conazoles possess at least one chiral center and thus exist as one (or more) pairs of enantiomers with differing biological properties. The determination of any enantioselective toxicity is an essential component for accurate risk assessment of chiral pesticides. Recently, metabolomics, or the quantitative measurement of a broad spectrum of metabolic responses of living systems in response to disease onset or genetic modification, has been employed to enable rapid identification of the mechanisms of toxicity for compounds of environmental concern, such as the enantiomers of chiral pesticides. In this study, we investigated the potential for this new technology to differentiate the toxicities of the enantiomers of triadimefon and other conazoles in rainbow trout using nuclear magnetic resonance (NMR) spectroscopy. Preliminary NMR data show a significant metabolic response in rainbow trout livers to racemic triadimefon, fed via gavage, as indicated by differences in the endogenous metabolite pattern from that of a control. This abstract has been reviewed and approved for presentation and publication by the U.S. EPA, but does not necessarily reflect U.S. EPA policy.
166 (LEH-1117-807098) PCB 84: Disposition and Toxicity.
Start time: 4:30 PM
Lehmler, H.1, Price, D.2, Birge, W.2, Robertson, L.1, Garrison, A.3, 1 University of Iowa, Department of Occupational and Environmental Health, Iowa City, Iowa, USA2 University of Kentucky, School of Biological Sciences, Lexington, Kentucky, USA3 National Exposure Research Laboratory, US Environmental Protection Agency, Athens, Georgia, USA
Nineteen of the 209 possible polychlorinated biphenyl (PCB) congeners exist as pairs of stable rotational isomers that are enantiomeric to each other. Although a racemic mixture of chiral PCBs is present in technical PCB mixtures, enantioselective processes may result in an enantiomeric enrichment of these PCBs in the environment. The enantiomeric enrichment of chiral PCB congeners has been reported in tissue and blood samples from wildlife and humans, but only limited information about the enantioselective disposition of individual, chiral PCB congeners is available for laboratory animals. Intraperitoneal administration of racemic 2,2',3,3',6-pentachlorobiphenyl (PCB 84) in untreated female C57Bl/6 mice resulted in a statistically significant enrichment of (+)-PCB 84 in brain, liver, lung, kidney and heart tissues six days after administration, whereas no enantiomeric enrichment was observed in the spleen. The highest enantiomeric fractions were found in the brain, an observation that is of particular concern because PCB 84 enantiomers are known to have different potencies in in vitro neurotoxicity studies. Both (+)- and (-)-PCB 84 increased [3H]phorobol ester binding in a concentration-dependent manner with (-)-PCB 84 being slightly more potent. Both PCB 84 enantiomers also inhibited microsomal 45Ca2+ uptake in a concentration-dependent manner, but no significant difference in the potency of the enantiomers was observed. These findings may have important implications for understanding the mechanism of neurotoxicity of chiral PCB congeners and further investigations of the disposition and toxicity of chiral PCBs are warranted (Supported by ES 012475 and ES 07380 from NIH; this abstract does not necessarily reflect USEPA policy).
167 (LAR-1117-855309) Enatiomeric Concentrations of Hexabromocyclododecane in Chesapeake Bay Fish.
Start time: 4:50 PM
Larsen, R1, Peck, A2, Liebert, D2, Richardson, K3, Davis, E1, 1 St. Mary's College of Maryland, St. Mary's City, MD, USA2 Hollings Marine Laboratory, Charlestown, SC, USA3 Chesapeake Biological Laboratory, Solomons, MD, USA
Commercial hexabromocyclododecane (HBCD) is a brominated flame retardant synthesized using a process that produces a racemic mixture of alpha, beta, and gamma diastereomers. This study exams the interspecies concentration, distribution and enantiomeric composition of the three stereoisomers. Fifty species-specific composites samples were made from 211 individual fish collected in the Chesapeake Bay and its' tributaries. The composite samples were soxhlet extracted and quantified for HBCDs on a chiral column equipped LC/MS/MS. Species analyzed included catfish, perch, bass, sunfish, eel, bluegill, trout, bullhead, and white sucker. These samples represent a variety of benthic and pelagic organisms, as well as trophic levels. Lipid normalized concentrations of HBCDs ranged from 10 to 410 ng g-1 for channel catfish, ND-300 ng g-1 for striped bass, and 6-110 ng g-1 for white perch. The magnitude of the HBCDs concentrations in channel catfish is linearly proportional (r2=0.78) to the alpha:gamma ratio, which implies differences in the bioaccumulative properties of the two steroisomers. This study provides some of the first evidence of HBCD contamination in U.S. and specifically Chesapeake Bay fisheries.
168 (MOR-1117-759673) Chiral polychlorinated biphenyls in the aquatic food web of Lac la Biche, Alberta.
Start time: 5:10 PM
Morrissey, Joshua1, Wong, Charles1, 1 University of Alberta, Edmonton, AB, Canada
Enantiomeric fractions (EFs) of chiral pollutants are useful indicators of biotransformation in the environment. The aquatic food web of Lac la Biche (LLB), Alberta has undergone significant changes, ranging from hypereutrophication to population loss of walleye from over-fishing. The dramatic decrease in the numbers of walleye has resulted in a population explosion of double-crested cormorants, which have replaced walleye as the top predator in this system. Population control measures are currently in place to reduce the numbers of double crested cormorants at LLB. Chiral polychlorinated biphenyls (PCBs) were studied in the aquatic food web of LLB in order to assess the changing dynamics of this food web. Invertebrates, forage fish (e.g., yellow perch, spottail shiners, white suckers), predatory fish (including northern pike) and cormorant eggs, chicks, and adults were collected in 2004. Samples were extracted for organochlorine pesticides and analyzed by chiral gas chromatography/mass spectrometry (GC/MS), while stable carbon and nitrogen ratios were used to determine feeding and trophic structure. Preliminary results which show racemic EFs of chiral PCBs in yellow perch indicate that stereoselective biotransformation of PCBs is not occurring in the lower food web of LLB, while possible changes in EF at higher trophic levels may indicate the occurrence of biotransformation in this food web.