Different Degrees Of Chlorination Research Articles

A new scheme of dispersive liquid-liquid microextraction of polychlorinated biphenyls having different degrees of chlorination from waters with subsequent identification by gas chromatography coupled with mass spectrometry

This study offers a theoretical rationale and experimental validation of extraction of 22 polychlorinated biphenyls (PCBs) having various degrees of chlorination (including five dioxin-like ones: PCB-105, PCB-118, PCB-156, PCB-157, and PCB-167) from waters of various salinity levels by dispersive liquid–liquid microextraction (DLLME) using various extractants and mixtures of aliphatic alcohols for additional dispersion, with subsequent identification by gas chromatography coupled with mass spectrometry. To optimize the conditions of DLLME and of concentrating PCBs of various degrees of chlorination, the experiment was planned via the three-factor Box–Behnken design (response surface methodology). Composition and ratios of components were found for the extractant mixture, and composition of the dispersive agent was optimized. Effective recovery of the 22 congeners from waters with salinity ranging between 1‰ and 22‰ was ensured by an extractant mixture consisting of chloroform, dichloromethane, and carbon tetrachloride and by a dispersive agent composed of acetone, ethyl acetate, ethyl alcohol, and isopropyl alcohol. The newly developed sample preparation scheme is compatible with gas chromatography coupled with mass spectrometry, and limits of detection and quantitation varied as follows: 0.0075–0.0150 and 0.025–0.050 µg/L, respectively. The newly developed assay allows to quantify the analytes at concentrations of 0.025–15 µg/L in waters, with recovery 90–105% and relative standard deviation 4–8%.

The effect of long-range atmospheric transport of organochlorine compounds by soil studies from Mongolia to the Arctic

The results of studies on the distribution regularities are presented for polychlorinated biphenyls (PCBs) of different degrees of chlorination and for organochlorine pesticides (OCPs): hexachlorobenzene (HCB), hexachlorocyclohexane (HCCH), and DDT with its metabolites in the soils along the Lena River valley and in background areas of Eastern Siberia and Mongolia. A statistically reliable correlation is found between the PCB–OCP and Corg concentrations. The highest levels of HCB are registered in the soils between 50 and 60° N. The concentrations of αand γ-HCCH increase reliably, while those of pp′-DDT and pp′-DDE decrease from south to north. A trend of the decrease in concentrations from Mongolia to the Laptev Sea is revealed for tri-, tetra-, and penta-chlorine-substituted PCB congeners. However, the soils sampled northwards from 60° N show a reliable increase in the concentrations of tetra-, penta-, and hexachlorine-substituted congeners.

In Situ Synthesis of Chlorinated Fullerenes by the High‐Frequency Furnace Method

AbstractExohedrally chlorinated fullerenes have been synthesized by in situ chlorination using the high‐frequency furnace method in the presence of carbon tetrachloride as reagent. In addition to the previously reported chlorinated non‐IPR (isolated pentagon rule) fullerene cages of C2nCl2m (n = 25, 27, 28, 30, 32 and 33, m = 2–6), a C68 and various new higher fullerenes including C2nCl2m with n = 36, 37 and 39 were present in the soot extracts in significant quantities, as shown by HPLC/off‐line mass spectrometric analyses. A more detailed analysis showed the presence of several species with the same carbon content that could arise from either the formation of different isomers or different degrees of chlorination.

The effects of individual PCB congeners on the soil bacterial community structure and the abundance of biphenyl dioxygenase genes

Polychlorinated biphenyls (PCBs) are toxic environmental contaminants that represent a class of 209 congeners characterized by different degrees of chlorination and substitution patterns. Most of experimental studies about microbial degradation of PCBs have been conducted on PCB mixtures, even though evidence accumulated in bacteria and other organisms shows that exposure to different congeners may have different biological effects. Microcosm experiments were conducted using aerobic agitated soil slurries individually exposed to PCB congeners with different degrees of chlorination: PCB-3, 15, 28, and 77, and the commercial mixture Aroclor 1242. After four weeks of incubation, PCBs were analyzed by gas chromatography/mass spectrometry (GC/MS) showing different transformation extents: With the exception of PCB-15 that was not significantly transformed (7%), biodegradation rates decreased with the degree of chlorination, from 75% for PCB-3 to 22% for PCB-77 and Aroclor 1242. The bacterial abundance, as measured by colony counting and 16S rDNA quantification by real-time PCR, was lower (of about 40%) in soil microcosms exposed to the higher-chlorinated congeners, PCB-28, PCB-77, and Aroclor 1242, as compared to non-exposed soils and soils exposed to the lower-chlorinated congeners, PCB-3 and PCB-15. The relative abundance of different taxonomic groups, as determined by real-time PCR, revealed an increase of β-Proteobacteria and Actinobacteria in all microcosms exposed to PCBs, as compared with non-exposed soil. In addition, exposure to PCB-77 and Aroclor 1242 resulted in a higher abundance of α-Proteobacteria and Acidobacteria. Globally, these results suggest that exposure to PCBs (and especially to higher-chlorinated congeners and Aroclor 1242) selected bacterial groups involving most known PCB degraders, i.e., β-Proteobacteria and Acidobacteria. The quantification of biphenyl dioxygenase (BPH) genes — involved in the aerobic degradation of PCBs — using real-time PCR showed that exposure to all PCB congeners and Aroclor 1242 resulted in a marked increase of two out of the four BPH genes tested, similarly suggesting the selection of PCB-degrading bacteria. This paper showed that exposure to different PCB congeners leads to different structures of the soil bacterial community and BPH genes expression patterns.

Nonenzymatic displacement of chlorine and formation of free radicals upon the reaction of glutathione with PCB quinones

The reactions of glutathione (GSH) with polychlorinated biphenyl (PCB) quinones having different degrees of chlorination on the quinone ring were examined. EPR spectroscopy and MS revealed 2 types of reactions yielding different products: (i) a nonenzymatic, nucleophilic displacement of chlorine on the quinone ring yielding a glutathiylated conjugated quinone and (ii) Michael addition of GSH to the quinone, a 2-electron reduction, yielding a glutathiylated conjugated hydroquinone. The pK(a) of parent hydroquinone decreased by 1 unit as the degree of chlorination increased. This resulted in a corresponding increase in the oxidizability of these chlorinated hydroquinones. The reaction with oxygen appears to be first-order each in ionized hydroquinone and dioxygen, yielding hydrogen peroxide stoichiometrically. The generation of semiquinone radicals, superoxide, and hydroxyl radicals was observed by EPR; however, the mechanisms and yields vary depending on the degree of the chlorination of hydroquinone/quinone and the presence or absence of GSH. Our discovery that chlorinated quinones undergo a rapid, nonenzymatic dechlorination upon reaction with GSH opens a different view on mechanisms of metabolism and the toxicity of this class of compounds.

Dichloromethane-enhanced negative ion chemical ionization for the determination of polychlorinated n-alkanes.

The use of dichloromethane/methane reagent gas mixtures is described as an alternative to conventional electron capture negative ionization for the determination of polychlorinated n-alkanes (PCAs). A nearly exclusive formation of [M + Cl]- adduct ions was observed suppressing the generation of other fragment ions. The resulting enhanced selectivity and sensitivity lowered quantification limits to 3 ng for a technical PCA mixture and 10.5-13.5 pg for single congeners. Response factors for congeners of different degrees of chlorination varied by not more than a factor of 2. Interferences from other polychlorinated compounds present in environmental samples such as toxaphene or chlordanes were suppressed by a factor of 5 or more. The technique was applied for the determination of the composition of technical PCA mixtures as well as for the analysis of PCAs in North Sea dab liver.

Effect‐directed fractionation and identification of cytochrome P4501A‐inducing halogenated aromatic hydrocarbons in a contaminated sediment

On the basis of a new fractionation method combined with in vitro ethoxyresorufin-O-deethylase (EROD) induction in a rainbow trout liver cell line (RTL-W1) and chemical analysis, halogenated aromatic hydrocarbons with dioxin-like activity were identified in a sediment extract from Bitterfeld, Germany. The fractionation method allowed a separation of different nonplanar and coplanar polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), dibenzo-p-dioxins (PCDDs), and dibenzofurans (PCDFs) with different degrees of chlorination. The dioxin-like activity at the investigated site could be quantitatively assigned to PCDD/Fs. Both PCBs and PCNs could be excluded as the cause of the measured effects on the basis of the fractionation procedure and bioanalytical results. Thus, the method allowed the chemical analysis to focus on PCDD/Fs, with significant reduction of the analytical expense. The EROD-induction potency of sediment-extract fractions was quantified, and toxicants were confirmed by the application of induction equivalent quantities on the basis of fixed-effect-level concentrations that exhibit 15% of the maximum induction by 2,3,7,8-tetrachlorodibenzo-p-dioxin. This approach was designed to minimize methodological limitations due to superimposing inhibitory effects.

Calculation of the polychlorinated terphenyl congener distribution and gas chromatographic retention behavior of selected single standards on four stationary liquid phases

The distribution of the 8557 theoretically possible structures of polychlorinated terphenyls (PCT) over the different degrees of chlorination and basic terphenyl backbones has been calculated and is presented in detail. As congeners missing chlorine atoms in an ortho position are suspected to be as noxious to organisms as dioxins, the number of these congeners is specified as well. The gas chromatographic retention behavior of 14 PCT single standards is studied on four stationary liquid phases for capillary columns (HP-Ultra 1, HP-5MS, RSL-300 and Polycarbonate) relative to 2,2′,3,4,4′,5,5′-heptachlorobiphenyl and shows no consequent separation of PCT in terms of the degree of chlorination. Individual congeners have been assessed for their suitability as internal standards in PCT analysis.

Perspectives in biodegradation of alkanes and PCBs

Abstract

Synthesis and three-dimensional structure of 3,5-dichloro-3,4,5,6-tetrahydropyridines

The reaction of N-chlorosuccinimide with 2,6-dimethyl-3,5-dimethoxycarbonyl-4-(2-difluoromethoxyphenyl)-1,4-dihydropyridine (phoridone) has been studied. Depending on the amount of chlorinating agent, 3,4,5,6-tetrahydropyridines with different degrees of chlorination were obtained. The three-dimensional structure of 3,5-dimethoxycarbonyl-4-(2-difluoromethoxyphenyl)-2-methyl-6-chloromethylene-3, 5-dichloro-3,4,5,6-tetrahydropyridine has been studied.

Concentrations and metabolism of PCBs in eggs of waterbirds on the German North Sea coast.

Among environmental chemicals found in top predators the polychlorinated biphenyls (PCB) often occur at high concentrations and are of toxicological relevance. Not only concentrations but also the composition of the PCB mixtures, which consist of many congeners of different degrees of chlorination, vary among species and sites. In this paper we show the interspecific variation in PCB concentrations and in the degree of metabolism of the PCB mixtures in eggs of 11 waterbird species breeding on the highly polluted German Wadden Sea coast, where the PCB contamination of birds has been increasing during the last decade. 14 refs., 2 tabs.

Toward a mechanistic understanding of PCDD biological activity based on molecular electrostatic potential modeling

The mechanism of action of polychlorinated dibenzo- p-dioxins (PCDDs) and related compounds has received extensive study but has not yet been completely elucidated. Most of the toxic responses and biological effects appear to be mediated by the binding to the Ah receptor. Our study is focused on the ligand-receptor complex which has a key role in the dioxin mechanism of action. In this paper we seek patterns in the molecular electrostatic potential (MEP) of PCDDs that can be related to their binding affinity. To this aim we analyse the three dimensional distributions of the MEP, obtained in the framework of the HF--SCF theory by ab initio calculations with the 3-21G basis set. A series of isomers showing a significant range of binding affinity values are studied: the choice of isomers belonging to the tetrachlorinated dibenzo- p-dioxin (TCDD) congener group allows us to study the effects of substitution patterns; the comparison with other PCDDs leads us to study the effects of different degrees of chlorination. On the basis of the significant electrostatic features we propose a structural hypothesis for the activity. Relevant information retained in the overall MEP distribution is summarized in a few descriptors, i.e. the MEP values in points properly located around the molecules. A good quantitative model is obtained which relates these descriptors with the experimental pEC 50 values.

Influence of coal chlorination conditions on aliphatic/aromatic selectivity

Two bituminous coals were chlorinated under various experimental conditions to find different degrees of chlorination and aliphatic/aromatic substitution ratios. The degree of chlorination and the atomic changes produced by chlorination were established by proximate and elemental analyses. Aliphatic/aromatic substitution ratios were determined by FT-i.r. spectroscopy. The chlorination degree was found to depend mainly on the reaction time, whereas the aliphatic/aromatic substitution ratio was related to the reagent and the reaction medium. The amount of chlorine remaining in the char after pyrolysis at 1173 K was related to the nature of the CCl bonds. TGA and DTG curves obtained during the pyrolysis of chlorinated samples allowed the two decomposition steps, associated with either aliphatic or aromatic chlorination, to be differentiated.

Relationship Between Chemical Structure of Chlorinated Benzenes and Their Effect on Hepatic and Serum Lipid Components in Rats

The study was performed to clarify the biological effects of chlorinated benzenes with different degrees of chlorination and different substituents. One series from monochlorobenzene to hexachlorobenzene was used to study the effect of the number of chlorine atoms. The second series was composed of p-amino-, hydroxy-, nitro- and methyl-chlorobenzene. Sprague Dawley male rats aged 4 weeks were fed diets containing the chlorinated benzenes at the level of 500ppm for 2 weeks.When the number of chlorine atoms in the benzene ring is over 4, the weight of the liver, lipid components in the liver and serum (total lipid, phospholipid and cholesterol), cytochrome P-450 and cytochrome c reductase significantly increased. However, the intensity of the biological effect was not always related to the number of chlorine atoms; the parameters were more markedly increased by pentachlorobenzene administration than by hexachlorobenzene administration.Vitamin A contents in the liver and serum were decreased by feeding of chlorinated benzenes, particularly pentachlorobenzene. Lipid peroxide in the liver was significantly elevated by pentachlorobenzene and monochlorobenzene administration, being accompanied by an increase of triglyceride and decreases of vitamin E and glutathione peroxidase.On the other hand, the biological effects of aniline, phenol, nitrobenzene and toluene were not markedly enhanced by chlorination.

Use of pattern recognition in the evaluation of PCDD and PCDF residue data from GC/MS analyses

We used the chemometric approach with SIMCA (soft independent modeling by class analogy) multivariate statistical programs, based on principal components modeling to examine complex PCDD and PCDF residues in environmental samples. This approach was employed to determine the acceptability of measured tetrachloro isotope ratios when three ion intensities, m +., (m+2) +., and (m+4) +., were measured by monitoring multiple ions. Isotope labeled internal standards and native compounds were examined. Principal components contain information about similarity of samples and variability in measurement. The data for the observed ion ratios were merged with the theoretical ion ratios and a calculated set of data that deviated from the theoretical values over a range of +/− 10 % for each ion pair. Thus the plot of principal components sample scores contains the error boundaries for accepting data that meet this quality assurance criterion and identifies the samples and calibration data that are within the acceptable range. In addition, GC/MS peaks having more than one constituent with different degrees of chlorination were readily detected. Residues of PCDDs in eggs of herring gulls ( Larus argentatus ) collected from colonies in the Great Lakes region in 1981 – 1984 were measured by GC/MS. Principal components modeling of the normalized residue data demonstrated that the sample residue profiles differed according to the sample's origin and that sample profiles remained remarkably similar over the 4-year period in which the samples were collected.

Compatibility among chlorinated polyethylenes

Compatibility among chlorinated polyethylenes with different degrees of chlorination has been identified by the transparency of blended films cast from solvent. Dynamic mechanical measurements have been used to check these observations. The heats of mixing of pairs of chlorinated octadecanes with different degrees of chlorination have been measured and shown to be positive. It has been found that in this system, which is dominated by dispersion forces, compatibility is determined by similarity of the equation-of-state parameters. The Flory equation-of-state theory without the interaction entropy parameter Q 12 generates a positive ΔG m and hence fails to predict compatibility. A positive Q 12 is needed to remedy this deficiency of the theory. This is in direct contrast to the negative Q 12 which is introduced in the systems which are dominated by specific interactions.

Effects of chlorinated paraffins on some drug-metabolizing enzymes in rat liver and in the Ames test.

Chlorinated paraffins (CP) consist of alkanes of the C10-C30 range with different degrees of chlorination. Commercially produced CP therefore consist of a variety of isomers with different chain lengths and chlorine content and a range or mean is given for each batch produced.KeywordsLiver MicrosomeSodium Dodecyl SulphateEpoxide HydrolaseStyrene OxideAmes TestThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Gas permeability of chlorinated polyvinyl trimethylsilane

By chlorination of polyvinyltrimethylsilane (PVTMS) by the action of molecular chlorine in a CCl 4 solution, initiated by visible light chlorinated PVTMS samples were obtained containing chlorine of n = 4·5, 18 and 78 Cl atoms per 100 Si atoms. Permeability factor P, coefficients of diffusion D and solubility σ of a number of gases (O 2, N 2, CH 4, C 2H 2, C 2H 4, SO 2, CH 3Cl, C 2H 3Cl) were determined with different degrees of chlorination. The rate of reduction of D with an increase in the degree of chlorination is dependent of the type of penetrating substance. For constant gases P decreases 4-fold with n = 78, whereas for SO 2, CH 3Cl and C 2H 3Cl P shows a much slighter dependence on n, which is due to the effect of the degree of chlorination of PVTMS on the coefficient of solubility of polar compounds.