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Comprehensive two-dimensional gas chromatography of the 209 polychlorinated biphenyls
Umeå University, Faculty of Science and Technology, Chemistry.
Umeå University, Faculty of Science and Technology, Chemistry.
Umeå University, Faculty of Science and Technology, Chemistry.
2003 (English)In: Journal of Chromatography A, ISSN 0021-9673, Vol. 1019, no 1-2, 111-126 p.Article in journal (Refereed) Published
Abstract [en]

Comprehensive two-dimensional gas chromatography (GC×GC) of the 209 polychlorinated biphenyls (CBs) was carried out using a longitudinally modulated cryogenic system (LMCS) and liquid carbon dioxide as cryogen. The effluent from a non-polar column was modulated and further separated on either a polar or a shape-selective second-dimension column. Five GC×GC column combinations were evaluated, with DB-XLB as the first column in each case. DB-XLB separates more congeners than any other GC column currently available. When combined with a biscyanopropyl siloxane (SP-2340 or BPX70) or smectic liquid crystal (LC-50) second-dimension column in a GC×GC system many additional CBs can be separated. In total, 176 and 181 of the 209 congeners were separated (Rs=0.5) on the column combinations DB-XLB/SP-2340 and DB-XLB/LC-50, respectively. Of the 136 CBs present in any Aroclor mixture at concentrations greater than 0.05% (w/w), 126 were resolved using either of these two column combinations. The seven frequently measured CBs 28, 52, 101, 118, 138, 153, 180, and the WHO-PCBs 77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169 and 189 were all separated from Aroclor CBs on the DB-XLB/LC-50 column set, whereas CBs 118 and 131 coeluted on the DB-XLB/SP-2340 column set. In addition, three technical CB formulations (Aroclors 1232, 1248 and 1260) and a seal blubber sample (Halichoerus grypus) from the Baltic Sea were analyzed. Similar peak patterns were found for Aroclor 1260 and the CBs in the seal blubber, facilitating use of this technical CB formulation to identify the CBs in the blubber by GC×GC. Individual CBs in environmental samples, such as seal blubber, may be identified semi-automatically by matching the samples GC×GC profiles to a template generated using a standard containing all 209 CBs. Using such a template, 64 CBs were identified in the grey seal blubber sample.

Place, publisher, year, edition, pages
2003. Vol. 1019, no 1-2, 111-126 p.
Keyword [en]
Gas chromatography, comprehensive two-dimensional, Baltic grey seal, Polychlorinated biphenyls, Aroclors
Identifiers
URN: urn:nbn:se:umu:diva-9222DOI: 10.1016/j.chroma.2003.08.100PubMedID: 14650609OAI: oai:DiVA.org:umu-9222DiVA: diva2:148893
Available from: 2008-03-12 Created: 2008-03-12 Last updated: 2009-12-07Bibliographically approved
In thesis
1. Analysis of PCBs with special emphasis on comprehensive two-dimensional gas chromatography of atropisomers
Open this publication in new window or tab >>Analysis of PCBs with special emphasis on comprehensive two-dimensional gas chromatography of atropisomers
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There are 209 PCB congeners, 136 of which have been found in technical PCB mixtures and hence may be found in the environment as a result of either intentional or unintentional release. The identification and quantification of the congeners are difficult due to analytical bias from coeluting PCBs and other persistent organic pollutants.

Among the 209 possible PCB congeners, 19 tri- and tetra-ortho chlorinated congeners exist in stable atropisomeric conformations. The racemization barrier were determined for twelve of the nineteen atropisomers and was found to be between 176-185 kJ × mol-1 and ca. 250 kJ × mol-1 for tri- and tetra-ortho PCB, respectively. Further, a buttressing effect of 6.4 kJ × mol-1 was observed for congeners with vicinal ortho-meta chlorines.

Comprehensive two-dimensional gas chromatography (GC×GC) was used to analyze the atropisomers and other PCBs. A Longitudinally Modulated Cryogenic System (LMCS) was used with liquid CO2 as cryogen. The LMCS was optimized for semi-volatile organic substances, primarily PCBs. The trap temperature was shown to be an important factor for the trapping and desorption efficiency, as was the thermal mass of the column used in the modulator region. A number of column sets were tested and the separation efficiency, congener resolution and analysis time was evaluated. Good separation of non- and mono-ortho PCBs and “bulk” PCBs (in a technical PCB) was obtained within 8 min using a smectic liquid crystal column (LC50) as the first and a nonpolar column as the second dimension column. Using a second column, an efficient nonpolar (DB-XLB) column, which separates many PCB congeners, were combined with a polar (cyanopropyl) or shape selective (LC50) second dimension column. As a maximum, 181 of the 209 congeners and 126 of the 136 Aroclor PCBs were resolved. The seven frequently measured PCBs (PCBs 28, 52, 101, 118, 138, 153 and 180) and all WHO-PCBs were separated from all other Aroclor PCBs.

Chiral PCBs are released into the environment as racemic mixtures. However, organisms have been shown to enantiomerically enrich many of the atropisomers, suggesting that enantioselective biotransformations occur. Non-racemic PCB enrichment has also been seen in mammalians including humans, which is of particular concern because of the potential health risk. An analytical procedure were therefore developed and used to determine the levels of atropisomeric PCBs, planar-PCBs (WHO-PCBs) and total PCBs in seals with different health status. GC×GC was used to separate the target PCBs from other PCBs and potential interferences. A chiral column (permethylated â-cyclodextrin) was used in combination with a polar or shape selective column and enantiomeric fractions (EFs) were determined for five atropisomeric PCBs, i.e. CBs 91, 95, 132, 149 and 174. Some atropisomers had EF that deviated largely from racemic. The deviation was larger in liver than blubber, indicating enantioselective metabolism. However, there was no selective passage of the studied atropisomeric PCBs across placenta and no selective blood-brain barrier. Similarly, no correlation between EFs and health status was observed, although there was a correlation between total PCBs and health status.

Place, publisher, year, edition, pages
Umeå: Kemi, 2003. 61 p.
Keyword
Environmental chemistry, PCB, Atropisomers, Chiral, GC×GC, Enantiomeric barriers, Seal, polar, shape selective, Cyclodextrin, 2D, ECD, FID, TOF-MS, Comprehensive two-dimensional GC, Miljökemi
National Category
Environmental Sciences
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-54 (URN)91-7305-475-5 (ISBN)
Public defence
2003-06-06, Umeå, 13:00 (English)
Available from: 2003-06-06 Created: 2003-06-06 Last updated: 2009-12-07Bibliographically approved
2. Trace analysis of dioxins and dioxin-like PCBs using comprehensive two-dimensional gas chromatography with electron capture detection
Open this publication in new window or tab >>Trace analysis of dioxins and dioxin-like PCBs using comprehensive two-dimensional gas chromatography with electron capture detection
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), two groups of struc-turally related chlorinated aromatic hydrocarbons, generally referred to as “dioxins” are of great concern due to their extreme toxicity and presence in all compartments of the environment. Since they occur at very low levels, their analysis is complex and challenging, and there is a need for cost-efficient, reliable and rapid analytical alternatives to the expensive methods in-volving use of gas chromatography high-resolution mass spectrometry (GC-HRMS). It is im-portant to routinely monitor food and feed items to detect contaminations at an early stage. For the regulation of dioxins and dioxin-like PCBs in food and feed according to current legis-lation, large numbers of samples have to be analysed. Furthermore, soils at many industrial sites are also contaminated with dioxins and need remediation. In order to optimize the cost-efficiency of reclamation activities it is important to acquire information about the levels and distribution of dioxins in the contaminated areas.

The aim of the studies underlying this thesis was to investigate the potential of comprehen-sive two-dimensional gas chromatography with a micro-electron capture detector (GC × GC-µECD) as a cost-effective method for analysing dioxins and dioxin-like PCBs in food, feed, fly ash and contaminated soils. Quantification studies of dioxins and dioxin-like PCBs were con-ducted and results were compared with GC-HRMS reference data. Generally, there was good agreement between both the congener-specific results and data expressed as total toxic equiva-lents (TEQs). The developed GC × GC-µECD method meets the European Community (EC) requirements for screening methods for control of dioxins and dioxin-like PCBs in food and feed. The presented results also indicate that GC × GC-µECD has potential to be used as a routine method for the congener-specific analysis of 2,3,7,8-PCDD/Fs and dioxin-like PCBs in matrices such as food and feed, fly ash and soil.

However, to fully exploit the potential of the GC × GC-µECD technique, it should be combined with a fast and cost-efficient sample preparation procedure. Therefore, a number of certified reference materials (CRMs) were extracted using a new shape-selective pressurized liquid extraction technique with integrated carbon fractionation (PLE-C), and the purified extracts were analysed for PCDD/Fs using GC × GC-µECD. The results compared well with the certified values of a fly ash and a sandy soil CRM, but they were much too high for a com-plex clay soil CRM. It was concluded that this combination of techniques was very promising for screening ash and highly permeable soils.

Further assessments and method revisions are still required before GC × GC-µECD can be used on a routine basis, and available software packages need to be refined in order to accelerate the data-handling procedures, which currently restrict the sample throughput.

Place, publisher, year, edition, pages
Umeå: Kemi, 2006. 43 p.
Keyword
Comprehensive two-dimensional gas chromatography, GC × GC, µECD, PCDDs, PCDFs, dioxins, dioxin-like PCBs, Pressurized liquid extraction, PLE, PLE-C, food, feed, fly ash, soil
National Category
Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-963 (URN)91-7264-234-3 (ISBN)
Public defence
2007-01-19, KB3B1, KBC, Umeå Universitet, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2006-12-29 Created: 2006-12-29 Last updated: 2012-06-07Bibliographically approved

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Danielsson, ConnyHaglund, Peter

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