Enantiomer separation of polychlorinated biphenyl atropisomers and polychlorinated biphenyl retention behavior on modified cyclodextrin capillary gas chromatography columns.

Seven commercially-available chiral capillary gas chromatography columns containing modified cyclodextrins were evaluated for their ability to separate enantiomers of the 19 stable chiral polychlorinated biphenyl (PCB) atropisomers, and for their ability to separate these enantiomers from achiral congeners, necessary for trace environmental analysis of chiral PCBs. The enantiomers of each of the 19 chiral PCBs were at least partially separated on one or more of these columns. Enantiomeric ratios of eleven atropisomers could also be quantified on six columns as they did not coelute with any other congener containing the same number of chlorine atoms, so could be quantified using gas chromatography-mass spectrometry. Analysis of a lake sediment heavily contaminated with PCBs showed enantioselective occurrence of PCB 91, proof positive of enantioselective in situ reductive dechlorination at the sampling site.

Flocculation of humic substances with metal ions as followed by capillary zone electrophoresis.

Humic and fulvic acids from various sources have been shown to give different electropherograms by capillary zone electrophoresis (CZE), depending on the pH of the electrolyte. This CZE work is extended here through investigations involving the titration of humic and fulvic acids with Fe(III) and Cu(II) cations. As increasing amounts of these cations were added to the humic substances (HUS), flocculation of metal-humic complexes occurred. This is believed to be caused by binding of the metal cations with negative carboxyl and phenolic sites on the HUS, resulting in a decrease of the repulsive forces that keep the HUS in a conformation more suitable for water solubility. The flocculated complexes were separated from the supernatant by centrifugation, and the supernatants were characterized as to total organic carbon (TOC) content, molecular weight (MW) using gel permeation chromatography, and average electrophoretic mobility (AEM) using CZE. The extent of flocculation correlated with both TOC and quantitative CZE measurements. The MW of the HUS remaining in solution actually decreased, presumably because of precipitation of larger molecules as they became insoluble because of reactions with the metals. Humic acids showed total precipitation of TOC with both metals at a concentration equivalent to their measured acidity. CZE demonstrated that certain fulvic acid fractions (low molecular weight phenolic acids) remained in solution even at high metal concentrations. In summary, changes in electrophoretic behavior of the soluble HUS could be related to changes in charge-to-mass ratios (charge densities) of both humic and fulvic acids with increasing metal cation concentration (neutralization). The copper treated HUS showed changes in their electrophoretic behavior even at low metal concentrations before flocculation, whereas the iron treated HUS flocculated uniformally over the range of added iron without significant changes in AEM. Thus these changes in CZE patterns illustrate different specific binding sites of the HUS for each metal.

Uptake and phytotransformation of o,p'-DDT and p,p'-DDT by axenically cultivated aquatic plants.

The uptake and phytotransformation of o,p'-DDT and p,p'-DDT were investigated in vitro using three axenically cultivated aquatic plants: parrot feather (Myriophyllum aquaticum), duckweed (Spirodela oligorrhiza), and elodea (Elodea canadensis). The decay profile of DDT from the aqueous culture medium followed first-order kinetics for all three plants. During the 6-day incubation period, almost all of the DDT was removed from the medium, and most of it accumulated in or was transformed by these plants. Duckweed demonstrated the greatest potential to transform both DDT isomers; 50-66% was degraded or bound in a nonextractable manner with the plant material after the 6-day incubation. Therefore, duckweed also incorporated less extractable DDT (32-49%) after 6 days than did the other plants. The capacity for phytotransformation/binding by elodea is between that of duckweed and parrot feather; approximately 31-48% of the spiked DDT was degraded or bound to the elodea plant material. o,p'-DDD and p,p'-DDD are the major metabolites in these plants; small amounts of p,p'-DDE were also found in duckweed (7.9%) and elodea (4.6%) after 6 days. Apparently, reduction of the aliphatic chlorine atoms of DDT is the major pathway for this transformation. This study, which provides new information on plant biochemistry as related to pollutant accumulation and phytotransformation, should advance the development of phytoremediation processes.

Uptake and phytotransformation of organophosphorus pesticides by axenically cultivated aquatic plants.

The uptake and phytotransformation of organophosphorus (OP) pesticides (malathion, demeton-S-methyl, and crufomate) was investigated in vitro using the axenically aquatic cultivated plants parrot feather (Myriophyllum aquaticum), duckweed (Spirodela oligorrhiza L.), and elodea (Elodea canadensis). The decay profile of these OP pesticides from the aqueous medium adhered to first-order kinetics. However, extent of decay and rate constants depended on both the physicochemical properties of the OP compounds and the nature of the plant species. Malathion and demeton-S-methyl exhibited similar transformation patterns in all three plants: 29-48 and 83-95% phytotransformation, respectively, when calculated by mass recovery balance during an 8-day incubation. No significant disappearance and phytotransformation of crufomate occurred in elodea over 14 days, whereas 17-24% degraded in the other plants over the same incubation period. Using enzyme extracts derived from duckweed, 15-25% of the three pesticides were transformed within 24 h of incubation, which provided evidence for the degradation of the OP compounds by an organophosphorus hydrolase (EC 3.1.8.1) or multiple enzyme systems. The results of this study showed that selected aquatic plants have the potential to accumulate and to metabolize OP compounds; it also provided knowledge for potential use in phytoremediation processes.

Occurrences and fate of DDT principal isomers/metabolites, DDA, and o,p'-DDD enantiomers in fish, sediment and water at a DDT-impacted Superfund site.

In the 1950s and 60s, discharges from a DDT manufacturing plant contaminated a tributary system of the Tennessee River near Huntsville, Alabama, USA. Regulatory action resulted in declaring the area a Superfund site which required remediation and extensive monitoring. Monitoring data collected from 1988, after remediation, through 2011 showed annual decreases approximating first-order decay in concentrations of total DDT and its six principal congeners (p,p'-DDT, o,p'-DDT, p,p'-DDD, o,p'-DDD, p,p'-DDE and o,p'-DDE) in filets from three species of fish. As of 2013, these concentrations met the regulatory requirements of 5 mg/kg or less total DDT for each fish tested. The enantiomer fractions (EF) of chiral o,p'-DDD in smallmouth buffalo and channel catfish were always below 0.5, indicating preferential decay of the (+)-enantiomer of this congener; this EF did not change significantly over 15 years. The often-neglected DDT metabolite p,p'-DDA was found at a concentration of about 20 µg/l in the ecosystem water.

Enantiomeric composition of chiral polychlorinated biphenyl atropisomers in aquatic bed sediment.

Enantiomeric ratios (ERs) for eight polychlorinated biphenyl (PCB) atropisomers were measured in aquatic sediment from selected sites throughout the United States by using chiral gas chromatography/mass spectrometry. Nonracemic ERs for PCBs 91, 95, 132, 136, 149, 174, and 176 were found in sediment cores from Lake Hartwell, SC, which confirmed previous inconclusive reports of reductive dechlorination of PCBs at these sites on the basis of achiral measurements. Nonracemic ERs for many of the atropisomers were also found in bed-sediment samples from the Hudson and Housatonic Rivers, thus indicating that some of the PCB biotransformation processes identified at these sites are enantioselective. Patterns in ERs among congeners were consistent with known reductive dechlorination patterns at both river sediment basins. The enantioselectivity of PCB 91 is reversed between the Hudson and Housatonic River sites, which implies that the two sites have different PCB biotransformation processes with different enantiomer preferences.

Simultaneous Determination of Ionization Constants and Isoelectric Points of 12 Hydroxy-s-Triazines by Capillary Zone Electrophoresis and Capillary Isoelectric Focusing.

Capillary zone electrophoresis (CZE) was used to separate and determine simultaneously the pK(1), pK(2), and pI values of 12 environmentally relevant hydroxytriazines (hydroxymetabolites of atrazine, terbuthylazine, simazine, and propazine and four (arylamino)-s-triazines) and observe the effects of the alkylamino and arylamino substituents on the measured values. Capillary isoelectric focusing (CIEF) methods were developed to measure the pI of these compounds and compare those values with the CZE-measured pI's. CZE and CIEF can provide accurate pK and pI values reasonably fast, and pI values measured by the two techniques agree. Knowledge of the pK and pI values of hydroxytriazines is important for an understanding of the binding mechanisms of these molecules in environmental matrices. Because the hydroxytriazines may exist as a myriad of species [Formula: see text] neutral, charged, zwitterionic, and keto-enol tautomeric [Formula: see text] depending on structure and pH, we briefly addressed the existence of these species relative to their electrophoretic analysis.

Enantiomeric composition of chiral polychlorinated biphenyl atropisomers in aquatic and riparian biota.

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.

Influence of environmental changes on degradation of chiral pollutants in soils.

Numerous anthropogenic chemicals of environmental concern--including some phenoxy acid herbicides, organophosphorus insecticides, polychlorinated biphenyls, phthalates, freon substitutes and some DDT derivatives--are chiral. Their potential biological effects, such as toxicity, mutagenicity, carcinogenicity, and endocrine disrupter activity, are generally enantiomer-selective, and different enantiomers are preferentially degraded (transformed) by micro-organisms in various environments. Here we use field and laboratory experiments to demonstrate that environmental changes in soils can alter these preferences, and to suggest that the preferences shift owing to different groups of related microbial genotypes being activated by different environmental changes. In Brazilian soils, almost all pasture samples preferentially transformed the non-herbicidal enantiomer of dichlorprop ((RS)-2-(2,4-dichlorophenoxy)propionic acid), while most forest samples either transformed the herbicidal enantiomer more readily or as rapidly as the non-herbicidal enantiomer. Organic nutrient enrichments shifted enantioselectivity for methyl dichlorprop ((RS)-methyl 2-(2,4-dichlorophenoxy)propionic acid) strongly towards preferentially removing the non-herbicidal enantiomer in soils from Brazil and North America, potentially increasing phytotoxicity of its residues relative to that of the racemate. Assessments of the risks chemical pollutants pose to public health and the environment need to take into account the chiral selectivity of microbial transformation processes and their alteration by environmental changes, especially for pesticides as up to 25 per cent are chiral.

Determination of perchlorate in tobacco plants and tobacco products.

Previous field and laboratory studies with vascular plants have shown that perchlorate is transported from perchlorate fortified soils and is accumulated in the plant tissues and organs. This paper contains results of preliminary investigations on the occurrence of perchlorate in tobacco plants grown in soils amended with a fertilizer whose nitrogen content is derived from naturally occurring sodium nitrate (Chile saltpeter). Ion chromatography (IC) and capillary electrophoresis (CE) were used for quantitative analysis, while nuclear magnetic resonance (NMR) spectroscopy was used for qualitative analysis of perchlorate. Results show that perchlorate is accumulated by tobacco plants into the leaves from soils amended with fertilizers that contain perchlorate. Also, perchlorate can persist over an extended period of time and under a variety of industrial processes as shown by its presence in off-the-shelf tobacco products including cigarettes, cigars, and pouch and plug chewing tobaccos in concentrations ranging from nd to 60.4 +/- 0.8 mg/kg on a wet weight basis.