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PubMed1980

Liquid chromatography with amperometric reaction detection involving electrogenerated reagents: applications with in-situ generated bromine.

We describe the use of electrogenerated reactants for continuous on-line reaction detection with thin-layer hydrodynamic amperometry. The reagent is introduced into the liquid-chromatographic column effluent at a constant rate by using controlled-current electrochemistry. After the effluent passes through a short reaction coil, the reagent concentration is monitored at the detector. Reaction of eluted compounds with bromine is signalled by changes in the current detected. The direct electrochemical control of the reagent concentration allows changes to be made, even during the course of obtaining a chromatogram. Depending on the specific reagent or reaction, the reagent is supplied either by addition of a second stream or by direct generation in the mobile phase. The latter configuration provides sufficient baseline stability to permit detection of the uptake of as little as 10 pmol of reagent bromine. The technique has been used to detect nanograms of underivatized fatty acids, prostaglandins, and phenols after separation by reversed-phase liquid chromatography.

Bromine↗
PubMed2005

Determination of the odor threshold concentrations of chlorobrominated anisoles in water.

Trihalophenols, which are drinking water disinfection byproducts (DBPs) formed by chlorination or chloramination practices, can be biomethylated into trihalogenated anisoles. These latter compounds have traditionally been suspected of causing odor episodes in drinking water around the world. The odor threshold concentration (OTC) of mixed chlorobrominated anisoles, which were previously synthesized, was determined by flavor profile analysis (FPA) performed by an experienced panel trained to identify odors and tastes in water. The odor threshold amount (OTA) was evaluated by using a gas chromatograph equipped with olfactometry (GC-O) and electron capture detectors (ECD). FPA results for mixed chlorobromoanisoles gave a theoretical OTCs range from 2 to 30 ng/L, the 2,6-diBr-3Cl-anisole being the most odorous compound. Rubber is the general descriptor described by panelists for these compounds, although earthy and musty are the following most cited descriptors.

Anisoles↗
PubMed2005

Screening of organic halogens and identification of chlorinated benzoic acids in carbonaceous meteorites.

The occurrence of halogenated organic compounds measured as a sum parameter and the evidence of chlorinated benzoic acids in four carbonaceous meteorites (Cold Bokkeveld, Murray, Murchison and Orgueil) from four independent fall events is reported. After AOX (Adsorbable organic halogen) and EOX (Extractable organic halogen) screening to quantify organically bound halogens, chlorinated organic compounds were analyzed by gas chromatography. AOX concentrations varying from 124 to 209 microg Cl/g d.w. were observed in carbonaceous meteorites. Ion chromatographic analysis of the distribution of organically bound halogens performed on the Cold Bokkeveld meteorite revealed that chlorinated and brominated organic compounds were extractable, up to 70%, whereas only trace amounts of organofluorines could be extracted. Chlorinated benzoic acids have been identified in carbonaceous meteorite extracts. Their presence and concentrations raise the question concerning the origin of halogenated, especially chlorinated, organic compounds in primitive planetary matter.

Carbon↗
PubMed2000

Application of a purge and trap TDS-GC/MS procedure for the determination of emissions from flame retarded polymers.

Emissions of volatile organic compounds (VOCs) from different thermoplastic polymers used in electrotechnical applications were investigated using a purge and trap procedure that involved adsorption on Tenax GR. Results were compared to those for an operating TV set monitored in a test chamber. The analyses were in both cases carried out using thermodesorption gas chromatography with mass spectrometric detection (TDS-GC/MS). Substances identified were monomers, volatile additives, or related compounds. Special attention was given to the detection of halogenated compounds. Their origin was studied using reference samples and synthetic standards.

Air Pollutants↗
PubMed2005

Kinetics and mechanisms of formation of bromophenols during drinking water chlorination: assessment of taste and odor development.

Halophenols are often reported as off-flavor causing compounds responsible for medicinal taste and odor episodes in drinking water. To better understand and minimize the formation of 2-bromophenol and 2,6-dibromophenol which have low odor threshold concentrations (OTCs, 30 and 0.5 ng/L, respectively) a kinetic data base for the chlorination and bromination of phenols was established by combination of kinetic measurements and data from literature. Second-order rate constants for the reactions of chloro- and bromophenols with chlorine and bromine were determined over a wide pH range. The second-order rate constants for bromination of phenols are about three orders of magnitude higher than for chlorination. A quantitative structure activity relationship (QSAR) showed a good comparability of second-order rate constants from this study with those published previously for different phenol derivatives. The quantification of product distribution of the formed halophenols demonstrated that chlorine or bromine attack in ortho position is favored with respect to the para position. A kinetic model was formulated allowing us to investigate the influence of chlorine dose and some water quality parameters such as the concentration of phenol, ammonia, bromide and the pH on the product distribution of halophenols. The kinetic model can be applied to optimize drinking water chlorination with respect to phenol-born taste and odor problems. In general, high chlorine doses lead to low concentrations of intermediate odorous chlorophenols and bromophenols. An increase in the ammonia or phenol concentration leads to a higher consumption of HOCl and therefore greater final concentration of intermediate bromophenols. The presence of higher bromide than phenol concentration also facilitates the rapid bromination pathway which leads to further bromination of 2,6-dibromophenol to higher brominated phenols. Laboratory-scale experiments on taste and odor formation due to the chlorination of phenol- and bromide-containing waters have confirmed the trend of the model calculations.

Bromine↗
PubMed2006

The synthesis and resolution of 2,2'-, 4,4'-, and 6,6'-substituted chiral biphenyl derivatives for application in the preparation of chiral materials.

Various routes were examined for the synthesis of chiral biphenyl species that are substituted at the 2,2', 4,4' and 6,6' positions. Because the biaryl bond is tetrasubstituted, many coupling reactions were not suitable. The most reliable coupling reaction proved to be the Ullmann, which gave the desired product in 82% yield. The products were required as the starting point for the preparation of chiral materials using these as the monomer. For this reason, a route was required that produced large quantities of both enantiomers. The two enantiomers were resolved at the penultimate step by the use of chiral HPLC. A complicating feature proved to be the necessity to have a reactive group at the 4,4' positions, which would permit polymerization though this point. Ultimately, we employed an Ullmann coupling on a dibrominated arene, which occurred selectively at the more hindered bromine by virtue of the directing effect of an ortho ester substituent.

Aniline Compounds↗
PubMedDate not supplied

Certain organochlorine and organobromine contaminants in Swedish human milk in perspective of past 20-30 years.

The investigations of organochlorine compounds in breast milk from women living in the Stockholm region started in 1967. The present study summarises the investigations of polychlorinated biphenyls (PCBs), naphthalenes (PCNs), dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), polybrominated diphenyl ethers (PBDEs) and pesticides (DDT, DDE, hexachlorobenzene, dieldrin) as well as methylsulfonyl metabolites of PCBs and DDE in human milk sampled during different periods up to 1997. During the course of 20-30 yr the levels of organochlorine compounds in human milk have decreased to various extent. A decrease to the half of the original concentration was attained in the range of 4-17 yr periods. On the contrary to the organochlorine compounds, the concentrations of PBDEs have increased during the period 1972-1997, indicating a doubling of the levels by 5 yr. The levels reflect the environmental contamination and background levels in the population. The accumulation and ongoing increase in the levels of PBDEs calls for immediate measures to stop the environmental pollution and human exposure to PBDEs.

Benzofurans↗
PubMed2004

Identification and quantification of pesticides, industrial chemicals, and organobromine compounds of medium to high polarity in the North Sea.

Solid-phase extraction of 20 L seawater samples enabled the enrichment and determination of a wide array of organic substances, including compounds of medium to high polarity, in the pg/L-range. A number of contaminants was detected and quantified throughout the North Sea, among them the pesticides dichlobenil (2,6-dichlorobenzonitrile), metolachlor and terbuthylazine as well as the industrial chemicals dichloropyridines (DCPy, 4 isomers) and nitrobenzene. Concentrations attained values up to 1.4 ng/L for dichlobenil, 0.83 ng/L for terbuthylazine, 0.61 ng/L for metolachlor, 0.13 ng/L for 2,6-DCPy, 4.37 ng/L for nitrobenzene and 1-8 ng/L for tris(chloropropyl)phosphates (TCPP). A number of North Sea water samples was screened for non-target compounds, revealing the presence of further contaminants, e.g., lindane and TCPP, as well as several biogenic and/or anthropogenic organobromine substances, among which bromoindols, -phenols and -anisoles were identified.

Bromine Compounds↗
PubMed1994

Polybrominated dibenzo-p-dioxins and dibenzofurans: literature review and health assessment.

Polybrominated dibenzo-p-dioxins (PBDDs) and dibenzofurans (PBDFs) occur as trace (ppb) contaminants in brominated flame retardants and are produced during combustion of these chemicals. They are also formed when organics are incinerated in the presence of bromine, e.g., in municipal and industrial incinerators and in internal-combustion engines. Combustion of organics in the presence of both bromine and chlorine results in the formation of mixed (i.e., bromo, bromo/chloro and chloro) halogenated dibenzo-p-dioxins and dibenzofurans (HDDs and HDFs). There are 4600 potential mixed congeners. The biological effects of PBDDs and PBDFs are similar, if not identical, to those of PCDDs and PCDFs. Both groups of compounds induce hepatic aryl hydrocarbon hydroxylase (AHH) and ethoxyresorufin-o-deethylase (EROD) in rats and cause wasting and thymic atrophy in rats and guinea pigs. Tetrabrominated dinenzo-p-dioxin (TBDD) and dibenzofuran (TBDF) are reproductive toxins in mice and produce skin lesions in the rabbit-ear acnegenic test. The brominated compounds appear to bind to the same cytosolic receptors believed to mediate the toxicities of the chlorinated analogs. When compared on a molar-concentration basis, the brominated compounds are equipotent to the chlorinated analogs. TBDD is absorbed after oral, dermal, or intratracheal administration in rats, stored in the liver and adipose tissue, and eliminated in the feces through biliary excretion. The biological half-lives of the brominated compounds appear to be somewhat shorter than those of the corresponding chlorinated species. The brominated compounds, like their chlorinated congeners, have the potential to cause dermal, hepatic, and gastrointestinal toxicities in humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2002

Effects of amidine derivatives on parasite-macrophage interaction and evaluation of toxicity.

In this work, the effect of amidine derivatives (with bromine and methoxy as substituents) in the "in vitro" parasite-macrophage interaction was evaluated. The potential toxicity was also analyzed. The results show that the methoxy-derivative was able to decrease the percentage of "in vitro" infection, being not hazardous to the host cell. Furthermore, experiments using Balb/c mice showed that this compound was very effective in avoiding infection in these animals. On the other hand, the compound with bromine as substituent was toxic to macrophages and unable to prevent infection in Balb/c mice. Pentamidine isethionate, used as reference drug, was not efficient in both experiments.

Amidines↗
PubMed1983

Transformations of 1- and 2-carbon halogenated aliphatic organic compounds under methanogenic conditions.

Several 1- and 2-carbon halogenated aliphatic organic compounds present at low concentrations (less than 100 micrograms/liter) were degraded under methanogenic conditions in batch bacterial cultures and in a continuous-flow methanogenic fixed-film laboratory-scale column. Greater than 90% degradation was observed within a 2-day detention time under continuous-flow methanogenic conditions with acetate as a primary substrate. Carbon-14 measurements indicated that chloroform, carbon tetrachloride, and 1,2-dichloroethane were almost completely oxidized to carbon dioxide, confirming removal by biooxidation. The initial step in the transformations of tetrachloroethylene and 1,1,2,2-tetrachloroethane to nonchlorinated end products appeared to be reductive dechlorination to trichloroethylene and 1,1,2-trichloroethane, respectively. Transformations of the brominated aliphatic compounds appear to be the result of both biological and chemical processes. The data suggest that transformations of halogenated aliphatic compounds can occur under methanogenic conditions in the environment.

Anaerobiosis↗
PubMed2005

FTIR and FT-Raman spectra, vibrational assignments and density functional theory calculations of 2,6-dibromo-4-nitroaniline and 2-(methylthio)aniline.

The FTIR and FT-Raman spectra of 2,6-dibromo-4-nitroaniline (2,6-DB4NA) in solid phase and 2-(methylthio)aniline (2-MTA) in liquid phase were measured. The geometry and normal vibrations have been obtained from the density functional theory (DFT) with the B3LYP method employing the 6-31G* basis set. Scale factors, which bring computational frequencies in closer agreement with the experimental data, have been calculated for predominant vibrational motions of the normal modes. The effects of the amino, bromine, nitro, thio and methyl substituents on vibrational frequencies have been investigated. The infrared and Raman spectra were also predicted from the calculated intensities. The observed and the calculated spectra were found to be in good agreement.

Aniline Compounds↗
PubMed2002

Pilot-scale studies on the effect of bromine addition on the emissions of chlorinated organic combustion by-products.

The addition of brominated organic compounds to the feed of a pilot-scale incinerator burning chlorinated waste has been found previously, under some circumstances, to enhance emissions of volatile and semivolatile organic chlorinated products of incomplete combustion (PICs) including polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/Fs). This phenomenon appears to be sensitive to temperature and combustion conditions. This paper reports on a study to evaluate the emissions of organic combustion by-products while varying amounts of bromine (Br) and chlorine (Cl) are being fed into a pilot-scale incinerator burning surrogate waste materials. The surrogate waste was fed at a constant molar halogen input rate, with varying Br/Cl molar ratios. In these tests, an approximately 30% decrease in the total PCDD/F concentrations due to the addition of Br was observed. This decrease appears to be a decrease only in the chlorinated dioxin and furan species; other halogenated dioxins and furans were formed instead. PCDD/F homologue distribution shifted towards the higher chlorinated species. Perhalogenated or nearly perhalogenated mixed bromo-chloro furans were also observed in quantities that could potentially account for the observed decrease in PCDDs/Fs. This research illustrates the need for careful trial burn planning if Br will be present in the facility's feed-stock during normal operation.

Benzofurans↗
PubMed1998

Metabolism of 2,2',4,4'-tetrabromodiphenyl ether in rat and mouse.

1. The distribution and excretion of orally administered 14C-labelled 2,2',4,4'-tetrabromodiphenyl ether (TBDE) have been studied in rat and mouse. 2. TBDE was efficiently absorbed and stored in adipose tissue where high concentrations were observed in both species. 3. In the rat, 86% of the dose was retained after 5 days, while 14% was excreted via the faeces and < 0.5% via the urine. 4. The mouse excreted 20% of the dose via the faeces and 33% via the urine, the latter as a hydrophilic and labile metabolite. 5. Metabolites covalently bound to macromolecules and lipids were noted in tissues and faeces from both species. 6. The major individual compound was parent TBDE in the faeces and tissues although small amounts of five hydroxylated metabolites were indicated by GC-MS. 7. In plasma from both rat and mouse only a few of the hydroxylated metabolites were present, indicating selective retention of these metabolites.

Administration, Oral↗