Tetrachlorobenzene Isomers Research Articles

Fatty Acid–Based pH‐Switchable Deep Eutectic Solvents for the Extraction and Preconcentration of Chlorobenzenes From Water Samples Followed by Gas Chromatography–Electron Capture Detection

ABSTRACTAn easy, safe, simple, and efficient pH‐switchable hydrophobic deep eutectic solvent (DES)‐based liquid‐phase microextraction was developed for the extraction of chlorobenzenes (CBs) from water samples followed by a gas chromatography–electron capture detector (GC–ECD). The switchability of the synthesized DESs was tested by changing the pH. The DES synthesized from thymol:octanoic acid (OA) in a molar ratio of 2:1 had the highest efficiency in extracting CBs from water samples. 1,4‐Dibromobenzene was used as internal standard (IS). The optimal conditions were established to be 20.0 µL of thymol:OA (2:1), 100 µL of 5 mol L−1 KOH, 100 µL of 5 mol L−1 HCl, 60 s of extraction time, and without salt addition. Under the optimum conditions, the calibration graphs were linear in the range of 0.005–150 µg L−1, and limits of detection were in the range of 0.001–0.03 µg L−1. The relative standard deviations, including intraday and inter‐day for 5.0 µg L−1 of dichlorobenzene isomers, 2.0 µg L−1 of trichlorobenzene and tetrachlorobenzene isomers, and 0.50 µg L−1 of pentachlorobenzene and hexachlorobenzene isomers in water with using IS, were in the range of 0.6%–3.2% (n = 7) and 3.8%–6.7% (n = 7), respectively. The accuracies, including inter‐day and intraday, were in the range of 93.5%–106.3% and 91.7%–109.4%, respectively.

Melting point, molecular symmetry and aggregation of tetrachlorobenzene isomers: the role of halogen bonding.

Tetrachlorobenzenes represent one of the best known, but not yet fully understood, group of isomers of the structure-melting point relationship. The differences in melting temperatures of these structurally related compounds were rationalized in terms of the hierarchy and nature of formed noncovalent interactions, and the molecular aggregation that is influenced by molecular symmetry. The highest melting point is associated with the highly symmetric 1,2,4,5-tetrachlorobenzene isomer. The structures of less symmetrical 1,2,3,4-tetrachlorobenzene and 1,2,3,5-tetrachlorobenzene, determined at 270 and 90 K, show a distinct pattern of halogen bonds, characterized by the different numbers and types of interactions. The evolution of Cl...Cl/H distances with temperature indicates the attractive character of intermolecular interactions and their importance to the structural and thermodynamic parameters of isomeric compounds. The favoured Cl...Cl halogen bonds were found to play a decisive role in differentiating the melting temperatures of tetrachlorobenzene isomers. It was also found that, besides the molecular symmetry and ability to form specific intermolecular interactions, both the type and the distribution of interactions are the important factors responsible for the melting behaviour of the studied isomers. The observed preferences, in tetrachlorobenzenes, for the formation of specific noncovalent interactions correspond to the distribution of calculated partial atomic charges and to the magnitudes of electrostatic potential on the molecular surfaces as well as correlate with the enthalpy of melting parameters.

Dechlorination of three tetrachlorobenzene isomers by contaminated harbor sludge-derived enrichment cultures follows thermodynamically favorable reactions

Dechlorination patterns of three tetrachlorobenzene isomers, 1,2,3,4-, 1,2,3,5-, and 1,2,4,5-TeCB, were studied in anoxic microcosms derived from contaminated harbor sludge. The removal of doubly, singly, and un-flanked chlorine atoms was noted in 1,2,3,4- and 1,2,3,5-TeCB fed microcosms, whereas only singly flanked chlorine was removed in 1,2,4,5-TeCB microcosms. The thermodynamically more favorable reactions were selectively followed by the enriched cultures with di- and/or mono-chlorobenzene as the main end products of the reductive dechlorination of all three isomers. Based on quantitative PCR analysis targeting 16S rRNA genes of known organohalide-respiring bacteria, the growth of Dehalococcoides was found to be associated with the reductive dechlorination of all three isomers, while growth of Dehalobacter, another known TeCB dechlorinator, was only observed in one 1,2,3,5-TeCB enriched microcosm among biological triplicates. Numbers of Desulfitobacterium and Geobacter as facultative dechlorinators were rather stable suggesting that they were not (directly) involved in the observed TeCB dechlorination. Bacterial community profiling suggested bacteria belonging to the phylum Bacteroidetes and the order Clostridiales as well as sulfate-reducing members of the class Deltaproteobacteria as putative stimulating guilds that provide electron donor and/or organic cofactors to fastidious dechlorinators. Our results provide a better understanding of thermodynamically preferred TeCB dechlorinating pathways in harbor environments and microbial guilds enriched and active in anoxic TeCB dechlorinating microcosms.

Diversity of dechlorination pathways and organohalide respiring bacteria in chlorobenzene dechlorinating enrichment cultures originating from river sludge.

Anaerobic reductive dechlorination of hexachlorobenzene (HCB) and three isomers of tetrachlorobenzene (TeCB) (1,2,3,4-, 1,2,3,5- and 1,2,4,5-TeCB) was investigated in microcosms containing chloroaromatic contaminated river sediment. All chlorobenzenes were dechlorinated to dichlorobenzene (DCB) or monochlorobenzene. From the sediment, a methanogenic sediment-free culture was obtained which dechlorinated HCB, pentachlorobenzene, three TeCB isomers, three trichlorobenzene (TCB) isomers (1,2,3-, 1,2,4- and 1,3,5-TCB) and 1,2-DCB. Dechlorination involved multiple pathways including the removal of doubly flanked, singly flanked and isolated chlorine substituents. 454-pyrosequencing of partial bacterial 16S rRNA genes amplified from selected chlorobenzene dechlorinating sediment-free enrichment cultures revealed the presence of a variety of bacterial species, including Dehalobacter and Dehalococcoides mccartyi, that were previously documented as organohalide respiring bacteria. A genus with apparent close relationship to Desulfitobacterium that also has been associated with organohalide respiration, composed the major fraction of the operational taxonomic units (OTUs). Another major OTU was linked with Sedimentibacter sp., a genus that was previously identified in strict co-cultures of consortia reductively dehalogenating chlorinated compounds. Our data point towards the existence of multiple interactions within highly chlorinated benzene dechlorinating communities.

Determination of Chlorobenzenes in Water Samples by Solid-Phase Disk Extraction and Gas Chromatography–Electron Capture Detection

A simple, rapid, sensitive and high throughput method is described, based on solid-phase disk extraction (SPDE) and gas chromatography-electron capture detection, for the determination of chlorobenzens (CBs) in water samples. The proposed SPDE sample pretreatment method was initially optimized and the optimum experimental conditions were found to be as follows: 500 mL water sample (pH 2.5) extracted and enriched by an Empore 3-stn C18 (octadecyl) SPE disk at flow rate of 5 to 50 mL/min, eluted by 5 mL of acetone and 3 × 5 mL of methylene dichloride. The linearity of the method ranged from 0.02 to 0.4 µg/L for dichlorobenzene isomers, 0.0022-0.044 µg/L for trichlorobenzene isomers, 0.005-0.01 µg/L for tetrachlorobenzene isomers and 0.00025 to 0.005 µg/L for pentachlorobenzenes and hexachlorobenzenes, with correlation coefficients ranging between 0.9991 and 0.9999. The limits of detection were in the low ng/L level, ranging between 0.05 and 4 ng/L. The recoveries of spiked CBs with the external calibration method at different concentration levels in deionized/distilled water, tap water and sea water samples were 99-115, 91-106% and 96-110%, respectively, and with relative standard deviations of 4.5-7.6, 4.2-6.8 and 3.6-6.6% (n = 5), respectively. It is concluded that this method can successfully be applied for the determination of CBs in deionized/distilled water, tap water and sea water samples.

Determination of chlorobenzenes in pure, tap, and sea water by static headspace gas chromatography‐electron capture detection

A simple, efficient, solvent-free, and commercial readily available approach for determination of 11 chlorobenzenes (CBs) in water samples using the static headspace (HS) sampling and gas chromatography-electron capture detector has been described. The proposed static HS sampling method was initially optimized and the optimum experimental conditions found were 10 mL water sample containing 20% (w/v) sodium chloride placed in a 20 mL vial and stirred at 70°C for 30 min. The linearity of the method ranged from 0.16 to 8.0 μg/L for dichlorobenzene isomers, 0.0176~0.88 μg/L for trichlorobenzene isomers, 0.004~0.2 μg/L for tetrachlorobenzene isomers, and from 0.001 to 0.05 μg/L for pentachlorobenzene and hexachlorobenzene, with correlation coefficients ranging between 0.9992 and 0.9999. The limits of detection were in the low μg/L level, ranging between 0.0002 and 0.04 μg/L. The relative recoveries of spiked CBs with external calibration or standard addition method at different concentration levels in pure, tap, and sea water samples were 83~116%, 89~108%, and 93~112%, respectively, and with relative standard deviations of 1.9~6.3%, 1.6~5.4%, and 2.5~5.7% (n = 5), respectively. It is concluded that this method can be successfully applied for the determination of CBs in pure, tap, and sea water samples.

Differential Acute Toxicity of Tetrachlorobenzene Isomers to Oligochaetes in Soil and Water: Application of the Critical Body Residue Concept

The acute, lethal potency of the 1,2,3,4-, 1,2,4,5- and 1,2,3,5-tetrachlorobenzene isomers was compared in the terrestrial and aquatic oligochaetes Eisenia andrei and Tubifex tubifex. 1,2,4,5-TeCB was neither lethal, nor produced any perceptible adverse effects, at lipid normalized concentrations predicted to be lethal according to the well-established critical body residue concept. If a narcotic is defined as a substance capable of inducing narcosis, rather than a substance displaying certain physical or chemical properties (e.g., log K(ow)), then we do not believe these findings challenge the critical body residue because by the former definition, 1,2,4,5-tetrachlorobenzene is not a narcotic.

Catalytic reduction of hexachlorobenzene and pentachlorobenzene by cobalt(I) salen electrogenerated at vitreous carbon cathodes in dimethylformamide

Abstract Cyclic voltammetry and controlled-potential electrolysis have been used to investigate the catalytic reduction of hexachlorobenzene and pentachlorobenzene by cobalt(I) salen that is electrogenerated at a carbon cathode in dimethylformamide containing 0.050 M tetramethylammonium tetrafluoroborate. Cyclic voltammograms for the reduction of cobalt(II) salen in the presence of either hexachlorobenzene or pentachlorobenzene show an enhanced cathodic peak for the catalyst–substrate reaction as well as loss of the anodic peak for reoxidation of cobalt(I) salen, revealing the effectiveness of the catalyst. However, cobalt(I) salen shows no catalytic activity toward tetrachlorobenzene or any less-chlorinated species. Controlled-potential electrolyses of cobalt(II) salen–hexachlorobenzene mixtures give both pentachlorobenzene and three isomers of tetrachlorobenzene, whereas bulk catalytic reduction of pentachlorobenzene affords three different tetrachlorobenzenes; for both substrates, substantial starting material remains unreduced. To account for the formation of the various products, a mechanistic scheme is proposed and discussed.

Part-per-trillion determination of chlorobenzenes in water using dispersive liquid–liquid microextraction combined gas chromatography–electron capture detection

In this study, a simple, rapid and efficient method, dispersive liquid–liquid microextraction (DLLME) combined gas chromatography–electron capture detection (GC–ECD), for the determination of chlorobenzenes (CBs) in water samples, has been described. This method involves the use of an appropriate mixture of extraction solvent (9.5 μl chlorobenzene) and disperser solvent (0.50 ml acetone) for the formation of cloudy solution in 5.00 ml aqueous sample containing analytes. After extraction, phase separation was performed by centrifugation and the enriched analytes in sedimented phase were determined by gas chromatography–electron capture detection (GC–ECD). Our simple conditions were conducted at room temperature with no stiring and no salt addition in order to minimize sample preparation steps. Parameters such as the kind and volume of extraction solvent, the kind and volume of disperser solvent, extraction time and salt effect, were studied and optimized. The method exhibited enrichment factors and recoveries ranging from 711 to 813 and 71.1 to 81.3%, respectively, within very short extraction time. The linearity of the method ranged from 0.05 to 100 μg l −1 for dichlorobenzene isomers (DCB), 0.002–20 μg l −1 for trichlorobenzene (TCB) and tetrachlorobenzene (TeCB) isomers and from 0.001 to 4 μg l −1 for pentachlorobenzene (PeCB) and hexachlorobenzene (HCB). The limit of detection was in the low μg l −1 level, ranging between 0.0005 and 0.05 μg l −1. The relative standard deviations (R.S.D.s) for the concentration of DCB isomers, 5.00 μg l −1, TCB and TeCB isomers, 0.500 μg l −1, PeCB and HCB 0.100 μg l −1 in water by using the internal standard were in the range of 0.52–2.8% ( n = 5) and without the internal standard were in the range of 4.6–6.0% ( n = 5). The relative recoveries of spiked CBs at different levels of chlorobenzene isomers in tap, well and river water samples were 109–121%, 105–113% and 87–120%, respectively. It is concluded that this method can be successfully applied for the determination of CBs in tap, river and well water samples.

Lion Akzo consolidating production in Yokkaichi

The concentration of dichloro- to hexachlorobenzene in the surficial bottom sediments in Ise Bay were determined as a preliminary study of the behavior of these compounds in this coastal environment. The sediment samples were collected from 10 stations on the west coast and in Yokkaichi Port in March 1987 and from 44 stations all over the bay in October 1987.1, 2- and 1, 3-Dichlorobenzene and 1, 2, 3- and 1, 2, 4-trichlorobenzene levels were highest in the vicinity of Yokkaichi Port and Tsu-Matsuzaka Port. Higher levels of these compounds were also found in the middle of the bay. The concentrations of tetrachlorobenzene isomers were generally low but they were also higher in the vicinity of the two ports. 1, 3, 5-Trichlorobenzene was higher only in the vicinity of Yokkaichi. The levels of these compounds were not higher around Nagoya City, the largest city in the bay. The stations with higher dichloro- and trichlorobenzenes concentrations in the middle of the bay covered the area where the sediment particle size was small. This was also the area where downward water flow was estimated to exit. These findings indicated that these congeners were adsorbed by suspended particulates and transported by water flow. The distribution patterns, therefore, could be explained by the following effects: the distance from the source, the horizontal transport caused by the river inflows and the sedimentation caused by downward water flow.Pentachlorobenzene concentration was very low and its distribution was not clear. Hexachlorobenzene had quite a different distribution pattern from other congeners, indicating that its sources were different.

Japan: Mitsubishi — carbon black

The concentration of dichloro- to hexachlorobenzene in the surficial bottom sediments in Ise Bay were determined as a preliminary study of the behavior of these compounds in this coastal environment. The sediment samples were collected from 10 stations on the west coast and in Yokkaichi Port in March 1987 and from 44 stations all over the bay in October 1987.1, 2- and 1, 3-Dichlorobenzene and 1, 2, 3- and 1, 2, 4-trichlorobenzene levels were highest in the vicinity of Yokkaichi Port and Tsu-Matsuzaka Port. Higher levels of these compounds were also found in the middle of the bay. The concentrations of tetrachlorobenzene isomers were generally low but they were also higher in the vicinity of the two ports. 1, 3, 5-Trichlorobenzene was higher only in the vicinity of Yokkaichi. The levels of these compounds were not higher around Nagoya City, the largest city in the bay. The stations with higher dichloro- and trichlorobenzenes concentrations in the middle of the bay covered the area where the sediment particle size was small. This was also the area where downward water flow was estimated to exit. These findings indicated that these congeners were adsorbed by suspended particulates and transported by water flow. The distribution patterns, therefore, could be explained by the following effects: the distance from the source, the horizontal transport caused by the river inflows and the sedimentation caused by downward water flow.Pentachlorobenzene concentration was very low and its distribution was not clear. Hexachlorobenzene had quite a different distribution pattern from other congeners, indicating that its sources were different.

Phototransformations of solid pentachlorophenol

The phototransformations of thin layers of pentachlorophenol (PCP), an insectide and herbicide, have been investigated in the laboratory in open air under irradiation at wavelengths >290 nm, i.e. corresponding to the sunlight UV region. The PCP disappearance rate was much higher when a 50 v / v% methanol / water mixture instead of pure methanol was used as the PCP deposition medium; changes in the product distribution also resulted although the products were the same. Analyses by GC / MS showed that tetrachlorophenols, hexachlorobenzene and pentachlorobenzene, in this order, were the monocyclic products that reached the highest amounts. Other C 6-membered products were trichlorophenol isomers and tetrachlorobenzene isomers. Hexachlorocyclopentadiene and a tetrachlorocyclo pentadiene isomer as well as five other C 5-membered cyclic products containing carbonyl groups, among which dichloromaleic anhydride was the most abundant, were also identified. Moreover, polychlorinated- p-dioxins and biphenylethers were formed, in particular octachlorodibenzo- p-dioxin reached a significant amount. With respect to PCP photodegradation in water the essential difference was the absence of products corresponding to the substitution of Cl by OH with possible subsequent oxidation to quinonic derivatives. Reactions based on the removal of one of the PCP chlorine atoms as the primary photochemical process are tentatively suggested to account for the formation of the main primary products. Consequences for the environment are also very briefly discussed.

Isomer-selective ionization of chlorinated aromatics with lasers for analytical time-of-flight mass spectrometry: First results for polychlorinated dibenzo-p-dioxins (PCDD), biphenyls (PCB) and benzenes (PCBz)

The combination of laser induced Resonance-Enhanced Multi-Photon Ionization (REMPI) and Time-Of-Flight mass spectrometry (TOF) represents a useful tool for detection of trace quantities of organic substances. REMPI spectra (i.e. laser UV spectra) as well as laser induced mass spectra of several aromatic compounds are presented. The possibility of isomer-selective ionization is demonstrated by REMPI ionization spectra of isomeric compounds: Spectra of three dichlorodibenzo-p-dioxin isomers, three tetrachlorobenzene isomers and three dichlorobiphenyl isomers are shown. Finally the potentiality of laser mass spectrometry in the field of environmental analysis is discussed.

Tetrachlorobenzenes: Evaluation of risks to health from environmental exposure in Canada

Abstract Tetrachlorobenzenes are included on the List of Priority Substances to be assessed under the Canadian Environmental Protection Act. Available data were critically evaluated to assess the human health effects of exposure to each of the isomers of tetrachlorobenzene in the Canadian environment. Adequate data on the carcinogenicity of each of the isomers of the tetrachlorobenzenes were not identified. The estimated average daily intakes of each of the tetrachlorobenzene isomers for the general population in Canada are 170 to 34,000 times less than the tolerable daily intakes derived from studies in experimental animals.

Enrichment and properties of an anaerobic mixed culture reductively dechlorinating 1,2,3-trichlorobenzene to 1,3-dichlorobenzene.

Hexachlorobenzene (HCB), pentachlorobenzene (QCB), all three isomers of tetrachlorobenzene (TeCB), 1,2,3-trichlorobenzene (1,2,3-TCB), and 1,2,4-TCB were reductively dechlorinated by enrichment cultures in the presence of lactate, glucose, ethanol, or isopropanol as the electron donor. The enrichment cultures originated from percolation columns filled with Rhine River sediment in which dechlorination of TCBs and dichlorobenzenes (DCBs) occurred. A stable consortium obtained by transfer on lactate as the energy and carbon source in the presence of 1,2,3-TCB dechlorinated this isomer stoichiometrically to 1,3-DCB. Dechlorinating activity could only be maintained when an electron donor was added. Lactate, ethanol, and hydrogen appeared to be the best substrates. Optimal temperature and pH for dechlorination were 30 degrees C and 7.2, respectively. The specificity of the enrichment on lactate and 1,2,3-TCB was tested after approximately 60 transfers (after 2.5 years). HCB and QCB were stoichiometrically dechlorinated to 1,3,5-TCB and minor amounts of 1,2,4-TCB. 1,3,5-TCB was the sole product formed from 1,2,3,5-TeCB, while 1,2,3,4-TeCB and 1,2,4,5-TeCB were converted to 1,2,4-TCB. 1,2,4-TCB, 1,3,5-TCB, and the three isomers of DCB were not dechlorinated during 4 weeks of incubation. For further enrichment of the 1,2,3-TCB-dechlorinating bacteria, a two-liquid-phase (hexadecane-water) system was used with hydrogen as the electron donor and 1,2,3-TCB or CO2 as the electron acceptor. Methanogens and acetogens were the major substrate-competing (H2-CO2) microorganisms in the two-liquid-phase system. Inhibition of methanogenesis by 2-bromoethanesulfonic acid did not influence dechlorination, and acetogens which were isolated from the enrichment culture did not have dechlorinating activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Etude thermodynamique des chlorobenzenes

The enthalpies of sublimation and fusion of all the tetrachlorobenzene isomers, and of pentachloro- and hexachloro-benzenes, and their triple point temperatures have been determined by sublimation calorimetry and differential thermal analysis. Using these thermodynamic quantities and corresponding values for the other chlorobenzenes (taken from the literature) we could explain, in some cases, the difference between the thermodynamic values of isomers and the molecular interactions in chlorobenzenes.

The distribution of chlorobenzenes in the bottom sediments of Ise bay

The concentration of dichloro- to hexachlorobenzene in the surficial bottom sediments in Ise Bay were determined as a preliminary study of the behavior of these compounds in this coastal environment. The sediment samples were collected from 10 stations on the west coast and in Yokkaichi Port in March 1987 and from 44 stations all over the bay in October 1987. 1, 2- and 1, 3-Dichlorobenzene and 1, 2, 3- and 1, 2, 4-trichlorobenzene levels were highest in the vicinity of Yokkaichi Port and Tsu-Matsuzaka Port. Higher levels of these compounds were also found in the middle of the bay. The concentrations of tetrachlorobenzene isomers were generally low but they were also higher in the vicinity of the two ports. 1, 3, 5-Trichlorobenzene was higher only in the vicinity of Yokkaichi. The levels of these compounds were not higher around Nagoya City, the largest city in the bay. The stations with higher dichloro- and trichlorobenzenes concentrations in the middle of the bay covered the area where the sediment particle size was small. This was also the area where downward water flow was estimated to exit. These findings indicated that these congeners were adsorbed by suspended particulates and transported by water flow. The distribution patterns, therefore, could be explained by the following effects: the distance from the source, the horizontal transport caused by the river inflows and the sedimentation caused by downward water flow. Pentachlorobenzene concentration was very low and its distribution was not clear. Hexachlorobenzene had quite a different distribution pattern from other congeners, indicating that its sources were different.

Partition coefficients of tetrachlorobenzene isomers between water and sodium dodecylsulfate micelles: relation to toxicity

Water-micelle partition coefficients for tetrachlorobenzenes were measured using a diffusion technique. The results show that the enchanced toxicity and tissue accumulation of the 1,2,4,5-isomer is not related to its lipophilicity.

A teratological evaluation and analysis of fetal tissue levels following administration of tetrachlorobenzene isomers to the rat.

Three tetrachlorobenzene (TCB) congeners (1,2,3,4- 1,2,3,5-, and 1,2,4,5-) were administered daily by gavage to pregnant Sprague-Dawley rats at levels of 50, 100, or 200 mg/kg from day 6 through day 15 of gestation. Mothers were sacrificed on day 21 of gestation and the pups removed by cesarian section for teratological evaluation. Administration of 1,2,3,4- and 1,2,3,5-TCB failed to alter maternal body weight, organ weights, hematological, or the biochemical parameters studied. The highest dose level of 1,2,4,5-tetrachlorobenzene caused maternal death in nine of ten animals. In addition it induced mixed function oxidases and increased serum cholesterol values at 50 and 100 mg/kg. There was a decrease in the number of fetuses at the highest dose levels of 1,2,3,4- and 1,2,3,5-TCB and at the lowest dose level of the 1,2,4,5- congener. None of the congeners produced any anomalies. There were no treatment-related histopathological changes in either the mothers or fetuses. Residues of all three congeners were found in maternal and fetal tissues but generally the amounts of the 1,2,4,5- isomer were about 100 times higher than the other two.

Conversion of [14C]pentachloronitrobenzene in onions

[U-14C]Pentachloronitrobenzene (purity >99.5%) was applied to soil (36.1 kg/ha) under outdoor conditions, and onion bulbs were planted. At harvest, the peeled onion bulbs contained <0.1 μg/g radioactive substances (equivalent to pentachloronitrobenzene), roots and peels 98.4 μg/g, and shoots 31.7 μg/g. About one-half to two-thirds of these residues were extractable by cold chloroform/methanol (1:1). The total metabolism rate was about 60% in the shoot extract and 80% in the peel-root extract. With the aid of authentic reference compounds, the following metabolites were identified from the shoot extract: pentachloroaniline (I), pentachlorophenyl-methylsulfoxide (II), pentachlorothioanisole (III), pentachlorobenzene (IV), and a tetrachloroaniline (V). From the root-peel extract, the following conversion products were identified: pentachloroaniline (I), pentachloroanisole (VI), pentachlorophenylmethylsulfoxide (II), pentachlorothioanisole (III), pentachlorobenzene (IV), pentachlorothiophenol (VII), pentachlorophenol (VIII), pentachlorophenylmethylsulfone (IX), pentachlorophenylacetate (X), two isomers of tetrachlorobenzene (XI and XII), and two isomers of tetrachloronitrobenzene (XIII and XIV). Additionally, structures are proposed for four minor conversion products (XV–XVIII) based on their mass spectra. These metabolites are derived from metabolites I–XIV by dechlorination, formylation, or introduction of the thiomethyl group. The residues extracted from peeled onion bulbs were too low for characterization.