Natalie Rosenfelder

Gas chromatography retention data of environmentally relevant polybrominated compounds

Polybrominated organic compounds are ubiquitous throughout the environment. This generic term comprises several classes of brominated flame retardants (e.g., polybrominated diphenyl ethers, polybrominated biphenyls, hexabromocyclododecane, dibromopropyltribromophenyl ether, 1,2-bis(2,4,6-tribromophenoxy)ethane) as well as a range of marine halogenated natural products (HNPs). Here we present gas chromatography retention times and elution orders (on DB-5) of 122 polybrominated compounds that may be found in food and environmental samples. Organobromine compounds in fish samples determined with gas chromatography interfaced to electron-capture negative ion mass spectrometry (GC/ECNI-MS) are discussed. The environmental relevance and important mass spectrometric features of the compounds are described as well. Our database aims to support the closer inspection and identification of peaks in gas chromatograms and to initiate dedicated screening for less frequently studied organobromines in samples.

Liquid chromatographic enantioseparation of the brominated flame retardant 2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE) and enantiomer fractions in seal blubber.

Enantioselective analyses of the chiral brominated flame retardant 2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE) are the focus of this work. High performance liquid chromatography (HPLC) equipped with a column that had a chiral stationary phase consisting of a modified cellulose derivative allowed for the fractionation of the enantiomers of DPTE. The enantiomeric excess was 98.2% for enantiomer 1 and 99% for enantiomer 2. Polarimetric measurements verified that the first eluting enantiomer originated from (-)-DPTE and the second peak originated from (+)-DPTE. Two gas chromatographic columns allowed for the direct enantioresolution of DPTE. The elution order of DPTE enantiomers was the same as observed in the chiral HPLC system ((-)-DPTE before (+)-DPTE). The best enantioseparation was achieved on a Chirasil-DEX CB column, which was used to analyze the enantiomer fractions of DPTE in blubber and brain samples of hooded seals (Cystophora cristata) and harp seals (Phoca groenlandica) from the Barents and Greenland Seas. Analyses were carried out by means of gas chromatography/electron capture negative ion mass spectrometry operated in the selected ion monitoring (GC/ECNI-MS-SIM) mode. In both matrices, only minute deviations from the racemate were observed (maximum +/-3% excess of (-)-DPTE). However, the samples from the Barents Sea were either racemic or showed a slight excess of (+)-DPTE (up to 2.5%), whereas all samples from the Greenland Sea contained a slight excess (up to 4%) of (-)-DPTE.

Gas chromatography/electron ionization-mass spectrometry-selected ion monitoring screening method for a thorough investigation of polyhalogenated compounds in passive sampler extracts with quadrupole systems

Nontarget analysis and identification of unknown polyhalogenated compounds is important in acquiring a thorough picture of the present pollution status as well as for identifying emerging environmental problems. Such analyses usually require the application of electron ionization mass spectrometry because the resulting mass spectra frequently allow for compound identification. When quadrupoles are used as mass separators, the full scan technique often suffers from low sensitivity along with nonspecificity for polyhalogenated trace compounds which often result in interference by matrix compounds. We have developed a novel nontarget gas chromatography/electron ionization-mass spectrometry-selected ion monitoring (GC/EI-MS-SIM) method that overcomes these sensitivity and selectivity issues. Our method is based on the fact that the molecular ions and isotope patterns of polyhalogenated compounds involve the most relevant primary information with regard to the structure of polyhalogenated compounds. Additionally, the retention times of polyhalogenated compounds generally increase with increasing molecular weight. The retention time range of polyhalogenated compounds was divided in three partly overlapping segments of 112 u (segment A: m/z 300-412; segment B: m/z 350-462; segment C: m/z 450-562) that were screened in eight GC runs consisting of 15 consecutive SIM ions. This method was tested with a passive water sampler extract known to contain over 30 polyhalogenated compounds according to the sensitive analysis by GC/electron capture negative ion (ECNI)-MS. While none of these polyhalogenated compounds could be detected by GC/EI-MS in full scan mode, our nontarget GC/EI-MS-SIM method allowed for the detection of 38 polyhalogenated compounds. Only seven could be identified by means of reference standards while more than 15 of the unknowns could be traced back to at least the class of compounds based on the mass spectrometric data from the nontarget SIM runs. All compounds identified originated from halogenated natural products. The nontarget GC/EI-MS-SIM method combines the high sensitivity obtainable with quadrupole systems for trace analysis with the structural information essential for the identification of unknown pollutants.

Gas chromatography coupled to electron capture negative ion mass spectrometry with nitrogen as the reagent gas – an alternative method for the determination of polybrominated compounds

Gas chromatography in combination with electron capture negative ion mass spectrometry (GC/ECNI-MS) is a sensitive method for the determination of polybrominated compounds in environmental and food samples via detection of the bromide ion isotopes m/z 79 and 81. The standard reagent gas for inducing chemical ionization in GC/ECNI-MS is methane. However, the use of methane has some drawbacks as it promotes carbonization of the filament and ion source. In this study, we explored the suitability of nitrogen as reagent gas for the determination of brominated flame retardants (polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs), allyl-2,4,6-tribromophenyl ether (ATE) and 2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE)) and halogenated natural products (for instance, methoxylated tetrabrominated diphenylethers and polybrominated hexahydroxanthene derivatives). An ion source temperature of 250 degrees C and a nitrogen pressure of 7 Torr in the ion source gave the highest response for m/z 79 and 81 of virtually all investigated polybrominated compounds. Using these conditions, nitrogen-mediated GC/ECNI-MS usually gave higher sensitivity than the method with methane previously used in our lab. In addition, the ion source was not contaminated to the same degree and the lifetime of the filament was significantly increased. Moreover, the response factors of the different polybrominated compounds with the exception of 2,4,6-tribromophenol were more uniform than with methane. Nitrogen is available at very high purity at relatively low price.

Stable carbon isotope analysis (δ13C values) of polybrominated diphenyl ethers and their UV-transformation products

Polybrominated diphenyl ethers (PBDEs) are frequently detected in food and environmental samples. We used compound specific isotope analysis to determine the δ(13)C values of individual PBDEs in two technical mixtures. Within the same technical product (DE-71 or DE-79), BDE congeners were the more depleted in (13)C the higher brominated they were. In contrast, the products of light-induced hydrodebromination of BDE 47 and technical DE-79 were more enriched in (13)C because of more stable bonds between (13)C and bromine. As a result, the δ(13)C values of the irradiated solution progressed diametrically compared to those of the technical synthesis. The ratio of the δ(13)C values of BDE 47 to BDE 99 and of BDE 99 to BDE 153 are thus suggested as indicators to distinguish native technical products from transformation products. Ratios <1 are typical for native congeners (e.g. in DE-71) while the reversed ratio (>1) is typical of transformation products.

Thorough analysis of polyhalogenated compounds in ray liver samples off the coast of Rio de Janeiro, Brazil

IntroductionFive liver samples of two different ray species (Gymnura altavela and Zapteryx brevirostris) off the coast of Rio de Janeiro, Brazil, were analyzed for their pollution with anthropogenic and naturally occurring organohalogen compounds.Material and methodsThe samples were extracted with accelerated solvent extraction, and after a clean-up procedure, organohalogen compounds were separated by a modified group separation on activated silica. Subsequent analyses were done by targeted and non-targeted gas chromatography–mass spectrometry in the electron capture negative ion mode.Results and discussion“Classic” organohalogen compounds such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and technical 1,1,1-trichloro-2,2-di(4-chlorophenyl)ethane (DDT) were detected and quantified. PCBs generally exceeded the parts per million level and represented up to 90% of the total contamination of the ray livers. High concentrations were also detected for p,p′-DDE. Non-targeted full scan investigations lead to the detection of an abundant trichlorinated compound which was identified as a new DDT metabolite in biota. Different PBDE congeners and several halogenated natural products were quantified as well. In addition, polychlorinated terphenyls were identified and analyzed in the two species. Moreover, both ray species showed different fatty acid patterns and stable carbon isotope signatures.ConclusionsThe two ray species showed high concentrations of organohalogen compounds in their liver tissue. Varied δ13C values by up to 3.1‰ indicated that the two ray species were living in different habitats.

Identification of the natural product 2,3,4,5-tetrabromo-1-methylpyrrole in Pacific biota, passive samplers and seagrass from Queensland, Australia.

Halogenated natural products (HNPs) are frequently detected in marine organisms. High HNP concentrations have previously been found in marine mammals from the Great Barrier Reef, Australia, including in the blubber of herbivorous dugongs (Dugong dugon). To identify the source of HNPs we initially focused on the analysis of Australian seagrass (Halophila ovalis) which serves as the principal food source for dugongs. GC/MS analysis of the seagrass indicated the presence of several organobromine compounds. One compound was identified as 2,3,4,5-tetrabromo-1-methylpyrrole (TBMP) by synthesis. Subsequent analysis of semipermeable membrane devices demonstrated that the photo-sensitive TBMP is widespread in the Great Barrier Reef (Queensland, Australia). The detection of larger TBMP concentrations in fish fillets from Chile and traces in mussels from New Zealand indicated that this potential HNP may be distributed throughout the Southern Pacific Ocean.

Polychlorinated terphenyl patterns and levels in selected marine mammals and a river fish from different continents

Polychlorinated terphenyls (PCTs) are a class of persistent organic pollutants which have been used from the 1920s to the 1980s for similar purposes as polychlorinated biphenyls (PCBs). Comparably little data was available on the PCT distribution in the environment mainly due to analytical difficulties in their determination. By means of a calculation algorithm recently developed we now studied the PCT pattern in individual marine mammal samples and one fish sample from different continents. Altogether, 97 PCTs were detected in eight samples and twelve to 66 tetra- to nonachloroterphenyl (tetra- to nonaCT) congeners were detected in individual samples. PCTs were present in all marine mammal samples which originated from four continents, but the PCT pattern was varied. TetraCTs were dominant in the sample from Africa, Australia, Spitsbergen (European Arctic) and in a sample from the Baltic Sea, heptaCTs in samples from the North Sea and octaCTs in a sample from Iceland. The abundance of sumPCTs relative to PCB 153, estimated from the GC/ECNI-MS response corrected for the degree of chlorination, ranged from 0.9 to 8.8%, corresponding with ~0.22-2.2% of the total PCB content. The highest PCT level detected was 980 mg/kg lipid in a harbour seal from the North Sea, Germany. The results from this study indicated that samples from certain areas, e.g. the North Sea may still be polluted with PCTs.