The High Resolution NMR Spectra of Pesticides. II. The DDT-Type Compounds

The high resolution nuclear magnetic resonance spectra of the DDT class of pesticides and related compounds are discussed, including a study of the resonances of the aromatic protons as they are affected by various substiluents. The CCl3 moiety on the α-carbon strongly deshields the ortho protons on the aromatic rings, and this deshielding effect is greatly enhanced by substitution of a chlorine ortho rather than para on the aromatic ring. These deshielding effects are explained by a consideration of the electronegativity of the substituents and the stereochemistry of the molecule. The chemical shifts and coupling constants are tabulated.

Isomers/enantiomers of perfluorocarboxylic acids: Method development and detection in environmental samples

Perfluoroalkyl substances are globally distributed in both urban and remote settings, and routinely are detected in wildlife, humans, and the environment. One of the most prominent and routinely detected perfluoroalkyl substances is perfluorooctanoic acid (PFOA), which has been shown to be toxic to both humans and animals. PFOA exists as both linear and branched isomers; some of the branched isomers are chiral. A novel GC-NCI-MS method was developed to allow for isomer/enantiomer separation, which was achieved using two columns working in tandem; a 30-m DB-5MS column and a 30-m BGB-172 Analytik column. Samples were derivatized with diazomethane to form methyl esters of the PFOA isomers. In standards, at least eight PFOA isomers were detected, of which at least four were enantiomers of chiral isomers; one chiral isomer (P3) was sufficiently separated to allow for enantiomer-fraction calculations. Soil, sediment and plant samples from contaminated locations in Alabama and Georgia were analyzed. P3 was observed in most of these environmental samples, and was non-racemic in at least one sediment, suggesting the possibility of chirally selective generation from precursors or enantioselective sorption. In addition, the ratio of P3/linear PFOA was inversely related to distance from source, which we suggest might reflect a higher sorption affinity for the P3 over the linear isomer. This method focuses on PFOA, but preliminary results suggest that it should be broadly applicable to other chiral and achiral perfluorocarboxylic acids (PFCAs); e.g., we detected several other homologous PFCA isomers in our PFCA standards and some environmental samples.

Pesticide Uptake Across the Amphibian Dermis Through Soil and Overspray Exposures

For terrestrial amphibians, accumulation of pesticides through dermal contact is a primary route of exposure in agricultural landscapes and may be contributing to widespread amphibian declines. To show pesticide transfer across the amphibian dermis at permitted label application rates, our study was designed to measure pesticide body burdens after two simulated exposure scenarios. We compared direct exposures, where amphibians were present when spraying occurred, to indirect exposures, where amphibians were exposed to soils after pesticide application. During summer 2012, we reared barking (Hyla gratiosa) and green treefrogs (H. cinerea) through 60-90 days post-metamorphosis at a United States Environmental Protection Agency research laboratory. We tested exposure for 8 h to five pesticide active ingredients (imidacloprid, atrazine, triadimefon, fipronil, or pendimethalin) in glass aquaria lined with soil in the laboratory. We quantified total pesticide body burden and soil concentrations using liquid chromatography-mass spectrometry. All individuals in both treatments had measurable body burdens at the end of the study. A randomized block design analysis of variance (n = 18) showed that body burdens (p = 0.03) and bioconcentration factors (BCFs) (p = 0.01) were significantly greater in the direct overspray treatment relative to the indirect soil spray treatment for both species and tested pesticides. BCFs ranged from 0.1 to 1.16 and from 0.013 to 0.78 in the direct and indirect treatments, respectively. Our study shows dermal uptake for multiple pesticides from both direct spray and indirect soil exposures and provides empirical support for the degree to which terrestrial phase amphibians have higher body burdens after overspray pesticide exposure.

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.

Enantioselective microbial transformation of the phenylpyrazole insecticide fipronil in anoxic sediments

Fipronil, a chiral insecticide, was biotransformed initially to fipronil sulfide in anoxic sediment slurries following a short lag period. Sulfidogenic or methanogenic sediments transformed fipronil with half-lives of approximately 35 and 40 days, respectively. In all microbially active sediment slurries tested, the transformation of fipronil to fipronil sulfide was enantioselective. In the sulfidogenic sediment slurry, the enantiomeric fraction (EF) of fipronil decreased from an initial racemic EF value of 0.46 to a value of 0.22 during the incubation period of active fipronil transformation, indicating preferential transformation of the S-(+)-enantiomer. A previously unidentified product, 5-amino1-[2,6-dichloro-4-(trifluoromethyl)-phenyl]-4-(trifluoromethylthio)-1-H-pyrazole-3-carboxyamide, or fipronil sulfide-amide, was detected in the sulfidogenic slurries and coincided with the loss of fipronil sulfide. Biota from methanogenic freshwater sediment slurries also transformed fipronil enantioselectively but with a preference for the R-(-)-enantiomer. In all microbially inhibited (autoclaved) sediment slurries tested, no changes in the enantiomeric fractions of fipronil were observed and only low levels (< 5% of the added fipronil) of the fipronil sulfide metabolite were detected. In defined (model) chemical experiments, solutions of pyrite (FeS2) and iron sulfide (FeS) non-enantioselectively transformed fipronil primarily to either 2,6-dichloro-4-(trifluoromethyl)-aniline or to fipronil sulfide and fipronil amide, respectively. This report provides the first experimental evidence of enantioselective microbial transformation of fipronil in a natural environment (soil, water, and sediment) as well as identification of a novel fipronil biotransformation product.

Toxicity of fipronil and its enantiomers to marine and freshwater non-targets

Fipronil is a phenylpyrazole insecticide used in agricultural and domestic settings for controlling various insect pests in crops, lawns, and residential structures. Fipronil is chiral; however, it is released into the environment as a racemic mixture of two enantiomers. In this study, the acute toxicity of the (S,+) and (R,-) enantiomers and the racemic mixture of fipronil were assessed using Simulium vittatum IS-7 (black fly), Xenopus laevis (African clawed frog), Procambarus clarkii (crayfish), Palaemonetes pugio (grass shrimp), Mercenaria mercenaria (hardshell clam), and Dunaliella tertiolecta (phytoplankton). Results showed that S. vittatum IS-7 was the most sensitive freshwater species to the racemic mixture of fipronil (LC50 = 0.65 microg/L) while P. pugio was the most sensitive marine species (LC50 = 0.32 microg/L). Procambarus clarkii were significantly more sensitive to the (S,+) enantiomer while larval P. pugio were significantly more sensitive to the (R,-) enantiomer. Enantioselective toxicity was not observed in the other organisms tested. Increased mortality and minimal recovery was observed in all species tested for recovery from fipronil exposure. These results indicate that the most toxic isomer of fipronil is organism-specific and that enantioselective toxicity may be more common in crustaceans than in other aquatic organisms.

Distribution of chiral PCBs in selected tissues in the laboratory rat

The enantiomeric enrichment of polychlorinated biphenyl (PCB) atropisomers has been reported in both wildlife and in humans. The biological processes causing this enrichment are only poorly investigated, a fact that limits the use of enantiomeric fractions (EFs) as a tool to study various processes of environmental relevance. To further understand these enantioselective processes, this study investigates the tissue distribution and EFs of some PCB atropisomers after administration of PCB mixtures to immature male Sprague-Dawley rats. The mixtures selected for this study, Aroclor 1254 and an environmental mixture extracted from Chlorofen-contaminated soil, are qualitatively different and are known to induce different groups of hepatic enzymes. Animals were sacrificed 6 days after dosing, PCBs were extracted, and, whenever possible, the EFs of PCBs 84, 91, 95, 149, 174, and 176 were determined by chiral gas chromatography. The EFs of PCB 95 (adipose tissue, liver, and skin) and PCB 149 (adipose tissue, liver, skin, and blood) in tissues from Aroclor 1254-treated animals differed significantly from EFs in the Aroclor standard, while only EFs of PCB 95 (blood) and PCB 174 (adipose tissue) in tissues from soil-extract-treated animals were different from those of the Chlorofen soil extract. PCB 149 in tissues from soil-extract-treated animals underwent no statistically significant enantiomeric enrichment. These differences in the EFs clearly suggest that the enantioselective enrichment of PCB atropisomers may correlate with exposure history, and with the induction of hepatic enzymes, and that EFs may be useful chemical markers of physiologic and biochemical changes following exposure to PCBs.

Estrogenic activity of dicofol with the human estrogen receptor: Isomer- and enantiomer-specific implications

Dicofol is a non-systemic acaricide/miticide currently registered in the US and Canada for use on a wide variety of crops. This agrochemical has been identified as a potential candidate substance for the United Nations Economic Commission for Europe (UN-ECE) Persistent Organic Pollutant (POP) Protocol and implicated as a potential "endocrine disrupting compound". The technical product is usually synthesized from technical DDT and consists of approximately 80% and 20% of p,p'- and o,p'-dicofol isomers. The o,p'-substituted isomer of dicofol is chiral and may have enantiomer-specific activity; however, the stereospecific activity of o,p'-dicofol has not been reported. In this study, we examined the isomer- and enantiomer-specific endocrine disruption potential of dicofol using yeast-based steroid hormone receptor gene transcription assay designed with the human estrogen receptor (hER). Estrogenic activity of (+)-17-beta estradiol (positive control), p,p'-dicofol, racemic o,p'-dicofol [(+/-)-o,p'-dicofol] and the individual o,p'-dicofol enantiomers was measured via quantification of beta-galactosidase. The (+/-)-o,p'- and p,p'-dicofol were weak estrogen mimics (EC(50): 4.2 x 10(-6) and 1.6 x 10(-6)M, respectively) relative to estradiol (3.7 x 10(-10)M). For o,p'-dicofol, the beta-galactosidase induction by (-)-o,p'-dicofol (EC(50): 5.1 x 10(-7)M) was greater than the racemic mixture. However, the (+)-o,p'-dicofol enantiomer was found to have negligible estrogenic activity. These data indicate that dicofol is a weak hER agonist due to activity of the achiral p,p'-isomer and (-)-o,p'-substituted enantiomer and emphasizes the influence of chemical structure and configuration on biological responses to exposure from chiral compounds.

Application of capillary electrophoresis to study the enantioselective transformation of five chiral pesticides in aerobic soil slurries

The enantiomers of five chiral pesticides of environmental interest, metalaxyl, imazaquin, fonofos (dyfonate), ruelene (cruformate), and dichlorprop, were separated analytically using capillary electrophoresis (CE) with cyclodextrin chiral selectors. For metalaxyl, imazaquin, and fonofos, aqueous slurries of soil samples from two sites in Georgia and one in Ohio were spiked with the racemate of each pesticide at 50-60 mg/L of aqueous phase of the slurry, and CE analyses were performed at various time intervals to determine enantiomer fractions (EF). Metalaxyl underwent enantioselective transformation; in one soil, the half-life of the target active R-(+)-enantiomer was 17 days while that for the S-(-)-enantiomer was 69 days. Transformation occurred more slowly in the other two soils but was still selective for the R-(+)-enantiomer. Imazaquin and fonofos exhibited nonselective enantiomer loss over their 3 months of incubation time; this could have been due to abiotic or nonselective microbial reactions. Ruelene and dichlorprop were transformed selectively in a variety of soils in a previously reported study (7) that showed the influence of environmental changes on the transformation of chiral pollutants in soils; analytical methods used in that study are reported here to further illustrate the application of CE. CE is shown to be a simple, efficient, and inexpensive way to follow the transformation of chiral pesticides in laboratory microcosms where concentrations can be made high enough (25-50 mg/L initial racemate concentration) for detection of residual parent enantiomers during most of the process.

Effects of PCB 84 enantiomers on [3H]-phorbol ester binding in rat cerebellar granule cells and 45Ca2+-uptake in rat cerebellum

There is evidence that polychlorinated biphenyl (PCB) congeners with ortho chlorine substituents have potential to cause neurotoxicity. Many PCB congeners implicated in these neurotoxic effects are chiral. It is currently unknown if the enantiomers of chiral PCB congeners have different neurotoxic effects. We herein report the effect of racemic 2,2',3,3',6-pentachlorobiphenyl (PCB 84) and its enantiomers on two neurochemical measures, protein kinase C (PKC) translocation as determined by [3H]-phorobol ester binding in cerebellar granule cells and Ca2+-sequestration as determined by 45Ca2+-uptake by microsomes isolated from adult rat cerebellum. Both (+)- and (-)-PCB 84 increased [3H]-phorobol ester binding in a concentration-dependent manner with (-)-PCB 84 being slightly more potent. Racemic PCB 84 was significantly more potent and efficacious than the pure enantiomers alone. (-)- and (+)-PCB 84 each inhibited microsomal 45Ca2+-uptake to a similar extent, whereas racemic PCB 84 was more potent and efficacious. These results indicate that PCB 84 enantiomers alone can have different potencies, and these may differ from that of the racemic mixture, observations that may have important implications for understanding the mechanisms of neurotoxicity of chiral PCB congeners.

Liquid chromatographic separation of the enantiomers of trans-chlordane, cis-chlordane, heptachlor, heptachlor epoxide and α-hexachlorocyclohexane with application to small-scale preparative separation

Analytical high-performance liquid chromatographic separations of the individual enantiomers of five polychlorinated compounds were obtained on polysaccharide stereoselective HPLC columns. The enantiomers of the pesticides trans-chlordane, cis-chlordane and heptachlor were separated on CHIRALCEL OD using a hexane mobile phase. The enantiomers of the heptachlor metabolite, heptachlor epoxide, were separated on CHIRALPAK AD using a methanol mobile phase. The enantiomers of alpha-hexachlorocyclohexane (alpha-HCH), were separated on CHIRALCEL OJ using a hexane/2-propanol mobile phase. Similar chromatographic conditions using preparative columns were used to isolate approximately 250 mg of each of the individual enantiomers. The purified individual enantiomers have been submitted for testing of their endocrine disruptor (ED) activity.

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.

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.

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.

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.

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.

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.

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.

Extraction and Determination of Selected Polycyclic Aromatic Hydrocarbons in Plant Tissues

A procedure has been developed for analysis of plant material for polycyclic aromatic hydrocarbons (PAHs). Sonication is used to extract the PAHs from homogenized plant material into acetonitrile and then the PAHs are partitioned into pentane. The pentane extract is fractionated on a micro silicic acid column and is analyzed by capillary gas chromatography with flame ionization detection. Overall method recoveries for 16 PAHs spiked into hybrid grain sorghum ranged from 45 to 90%, with relative standard deviations ranging from 3 to 38% and averaging 17%. This method can be used to measure PAHs in hybrid grain sorghum, fescue grass, and similar plants at the 25 μ/kg level. The procedure was applied to a preliminary study of PAH uptake by sorghum and fescue irrigated with secondary treated municipal wastewater spiked with 5 PAHs. Accumulation of fluoranthene and pyrene by fescue and hybrid grain sorghum from the PAH-contaminated irrigation water was apparent.