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At least 163 records · Page 9Linked to original sources
PubMed1979

Determination of halogenated organic compounds and mutagenicity testing of spent bleach liquors.

The content of organohalogenated compounds in spent bleach liquor from different bleaching stages in a sulphate and a sulphite plant has been determined by a combination of glass capillary gas chromatography, gas-liquid chromatography/mass spectrometry and neutron activation analysis. Several compounds which have not been reported before have been identified including halogenated derivatives of dimethyl-propylnaphthalenes and alkylated catechols. The unconcentrated effluents, non-polar and total extracts were tested for mutagenic activity with Ames' Salmonella test. Spent bleach liquors from most bleaching stages as well as the total effluents contained mutagenic compounds. Addition of liver microsomes for metabolic activation reduced the mutagenic activity in all stages except for the first chlorination stage in the sulphate plant. Two isomers of chloro-, bromo-, and dichloro-p-cymene previously determined in effluents from bleaching plants were synthesized from the parent molecule. Both bromo- and dichloro-p-cymene exhibited weak mutagenic activity in the Salmonella test system. Liver microsomes reduced the effect slightly. The chlorinated cymenes were found to account for up to 18% of the total organically-bound chlorine in the non-polar extracts.

Chemical Industry↗
PubMed2003

Degradation of halogenated aliphatic compounds utilizing sequential anaerobic/aerobic treatments.

The objective of this research was to determine if either methanogenic or sulfidogenic reductive dechlorination could survive an alternating anaerobic/aerobic sequence to biologically transform halogenated aliphatic hydrocarbons (HACs), specifically tetrachloroethylene (PCE), trichloroethylene (TCE), cis-1,2 dichloroethylene (cDCE), trans-1,2 dichloroethylene (tDCE), 1,1 dichloroethylene (1, 1DCE) and vinyl chloride (VC). This ability was considered to be a necessary prerequisite for complete anaerobic/aerobic mineralization of halogenated aliphatic hydrocarbons by a single microbial consortia. Chlorinated solvents, which are among the most common groundwater contaminants, have been partially dechlorinated using single-stage anaerobic environmental treatment strategies. Various types of bacteria typically reductively dechlorinate PCE and TCE to cDCE and VC in an anaerobic environment, including methanogens, sulfidogens, and homoacetogens. The problem lies in the fact that reductive dechlorination typically leads to an accumulation of daughter compounds (cDCE, VC) which are more toxic than their parent compounds (PCE, TCE). Furthermore, PCE and (to a lesser extent) TCE, are resistant to dechlorination in aerobic environments. In contrast, VC and cDCE are readily oxidized co-metabolically in an aerobic environment by methanotrophic bacteria, and others using oxygenases (e.g. toluene oxidizers). Results from this research showed that both methanogenic and sulfidogenic reductive dechlorination could resume after transient exposures to both oxygen and hydrogen peroxide (H2O2). In fact, for cycles as frequent as 10 days between aerobic treatment cycles, reductive dechlorination was observed to resume at rates at least as rapid as microcosms not exposed to aerobic treatments.

Bacteria, Aerobic↗
PubMed2001

Development and evaluation of a calibration gas generator for the analysis of volatile organic compounds in air based on the injection method.

The development and operational evaluation of a calibration gas generator for the analysis of volatile or ganic compounds (VOC) in air is described. Details of the construction, as well as of the evaluation of the apparatus are presented here. The performance of the test gas generator is validated both by on-line GC analysis of the calibration gas produced and by off-line analysis of adsorptive samples taken from the generated calibration gas. Both, active and passive sampling have been used, and the results demonstrate the excellent accuracy and precision of the generated test gas atmosphere: For the 11 investigated organic compounds (aromatic and halogenated compounds), the found values were in most cases within 5% of the target value with a reproducibility of better than 3% RSD (as determined by the analysis of the sampled adsorbent tubes). Custom made adsorbent tubes were used for active and passive sampling and in both cases were analysed by thermal-desorption GC. Particularly the combination of passive sampling and thermodesorption-GC analysis offers significant advantages over the commonly used active sampling on activated charcoal, followed by CS2 desorption in terms of avoidance of hazardous solvents, potential for automation and improved detection limits. Both sampling techniques are capable for monitoring VOCs at concentrations and under conditions relevant for workplace monitoring.

Adsorption↗
PubMedDate not supplied

Comparative effects of hexachloro- and hexabromobenzene on hepatic monooxygenase activity of male and female rats.

Male and female Sprague-Dawley rats were treated once with either crude or purified hexachlorobenzene (HCB) or crude or purified hexabromobenzene (HBB) at 150 mg/kg, intraperitoneally. Examination of hepatic microsomes 4 d later revealed an increase in cytochrome P-450 levels in both HCB- and HBB-pretreated animals. HBB produced a slight but statistically significant hypsochromic shift. Both HCB and HBB produced an increase in benzphetamine N-dealkylation: HCB produced a greater effect than HBB, and male rat microsomes produced more HCHO than female rat microsomes from the N-demethylation of benzphetamine. HCB and HBB both enhanced ethoxycoumarin and ethoxyresorufin O-dealkylation. Liver-to-body weight ratios were not significantly affected by pretreatment with either halogenated compound. There appeared to be no difference between the crude and purified halogenated compounds. Electrophoresis of microsomes from male rats pretreated with purified HBB indicated the presence of a band at 53,000 daltons, which was also seen in microsomes from rats pretreated with 3-methylcholanthrene. This band was absent in microsomes from rats pretreated with phenobarbital. Evidence from other laboratories has demonstrated the mixed type of P-450(s) induction after HCB administration, as does this report using enzymic and electrophoretic data.

Animals↗
PubMed1992

[Halogenated organic compounds in swimming pool water].

18 different swimming pool waters in the Bonn-Rhein-Sieg area were analysed for trihalogenmethanes, halogenated acetic acids, 2,2-dichloropropionic acid, dihalogenacetonitriles and chloral hydrate. Most substances mentioned above were determined in almost every sample reaching total concentrations up to 538 micrograms/l. Considering the results one can see that some of the main pollutants are polar organic compounds like di- and trichloroacetic acid as well as chloral hydrate.

Acetonitriles↗
PubMed2002

Solid-phase microextraction coupled with atomic emission spectroscopy--rapid screening for volatile chlorinated compounds.

Solid-phase microextraction (SPME) coupled with atomic emission spectroscopy was evaluated as a rapid screening tool for volatile halogenated compounds in water samples. After extraction, the SPME fiber was introduced to the injector where the analytes were rapidly and efficiently desorbed. The analytes entered the detector over a short period of time and produced one well-defined analyte signal. Element selective responses were measured to confirm the presence and to roughly estimate the content of volatile compounds. The total time for extraction and detection was approximately 5 min, which makes this method a rapid and promising technique for determination of total amount of volatile halogenated compounds. The proposed technique may prove useful as a screening test in order to pinpoint the samples that need further assessment by capillary gas chromatography.

Chemistry Techniques, Analytical↗
PubMed1994

Genetics and biochemistry of dehalogenating enzymes.

Microorganisms that can utilize halogenated compounds as a growth substrate generally produce-enzymes whose function is carbon-halogen bond cleavage. Based on substrate range, reaction type and gene sequences, the dehalogenating enzymes can be classified in different groups, including hydrolytic dehalogenases, glutathione transferases, monooxygenases and hydratases. X-ray crystallographic and biochemical studies have provided detailed mechanistic insight into the action of haloalkane dehalogenase. The essential features are nucleophilic substitution of the halogen by a carboxylate group and the presence of a distinct halogen binding site, formed by tryptophan residues. This review summaries current knowledge on a variety of other dehalogenating enzymes and indicates the existence of a widespread and diverse microbial potential for dechlorination of natural and xenobiotic halogenated compounds.

Amino Acid Sequence↗
PubMed2004

Optimization of dynamic headspace extraction of the edible red algae Palmaria palmata and identification of the volatile components.

A new extraction method was applied to the volatile compounds of Palmaria palmata. Dynamic headspace was optimized according to an experimental design, and descriptive sensory analysis and intensity and similarity tests were performed for each extract to assess their respective representativeness. Results showed that extract obtained with crushed algae after a 30 min purge was the most representative. GC-MS analysis was then performed on this extract to identify the volatile components. Seven halogenated compounds, seven aldehydes, two ketones, three alcohols, and four miscellaneous compounds were identified. Among them, halogenated compounds were the most characteristic of red algae, and more particularly, iodoethane and iodopentane, which had yet been found in other seaweeds.

Aldehydes↗
PubMed1976

[Biotransformation of halogen anesthetics and liver toxicity].

The authors attempt to explain halothane-induced hepatitis by a mechanism involving direct toxicity of a metabolite of this halogen compound. This implies a genetically determined metabolic disturbance or an increase in metabolic rate through previous enzyme induction (repeated anesthesia with halogen compounds).

Anesthetics↗