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Analysis of PCBs with special emphasis on comprehensive two-dimensional gas chromatography of atropisomers
Umeå University, Faculty of Science and Technology, Chemistry.
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 [en]
Environmental chemistry, PCB, Atropisomers, Chiral, GC×GC, Enantiomeric barriers, Seal, polar, shape selective, Cyclodextrin, 2D, ECD, FID, TOF-MS, Comprehensive two-dimensional GC
Keyword [sv]
Miljökemi
National Category
Environmental Sciences
Research subject
Analytical Chemistry
Identifiers
URN: urn:nbn:se:umu:diva-54ISBN: 91-7305-475-5 (print)OAI: oai:DiVA.org:umu-54DiVA: diva2:143766
Public defence
2003-06-06, Umeå, 13:00 (English)
Available from: 2003-06-06 Created: 2003-06-06 Last updated: 2009-12-07Bibliographically approved
List of papers
1. Determination of the rotational energy barriers of atropisomeric polychlorinated biphenyls
Open this publication in new window or tab >>Determination of the rotational energy barriers of atropisomeric polychlorinated biphenyls
1999 In: Fresenius Journal of Analytical Chemistry, Vol. 364, no 3, 219-223 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:umu:diva-4598 (URN)
Available from: 2003-06-06 Created: 2003-06-06Bibliographically approved
2. Effects of temperature and flow-regulated carbon dioxide cooling in longitudinally modulated cryogenic systems for comprehensive twodimensional gas chromatography
Open this publication in new window or tab >>Effects of temperature and flow-regulated carbon dioxide cooling in longitudinally modulated cryogenic systems for comprehensive twodimensional gas chromatography
2002 In: Journal of Chromatography A, Vol. 962, 127-134 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:umu:diva-4599 (URN)
Available from: 2003-06-06 Created: 2003-06-06Bibliographically approved
3. Shape selectivity: A key factor in comprehensive two-dimensional gas chromatographic analysis of toxic PCBs
Open this publication in new window or tab >>Shape selectivity: A key factor in comprehensive two-dimensional gas chromatographic analysis of toxic PCBs
2001 (English)In: Journal of Microcolumn Separations, ISSN 1040-7685, E-ISSN 1520-667X, Vol. 13, no 7, 306-311 p.Article in journal (Refereed) Published
Abstract [en]

A number of toxic planar PCBs, that is, PCB 77, 105, 118, 126, 156, and 169, were successfully separated from other PCB congeners present in technical PCB formulations using comprehensive GC×GC. The planar PCBs were selectively retained using a liquid crystal column, which was used as the first-dimension column. A short and narrow bore (0.25 m×0.1 mm) nonpolar 5%-phenyl-methylpoly-siloxane column was used as the second-dimension column. A longitudinally modulating cryogenic system (LMCS) was used to modulate the first-dimension signal. Since the planar PCBs elute from the first column at relatively high oven temperatures they were rapidly eluted from the second column. Altogether, this resulted in a significant peak sharpening, and a 20-fold increase in the signal-to-noise ratio, as compared to standard one-dimensional GC. This column set also seems to separate seven frequently measured congeners, that is, PCBs 28, 52, 101, 118, 138, 153, and 180, from other major PCB congeners.

Keyword
comprehensive two-dimensional gas chromatography, fast analysis, peak compression, shape selectivity, toxic PCBs
Identifiers
urn:nbn:se:umu:diva-8877 (URN)10.1002/mcs.10011 (DOI)
Available from: 2008-02-19 Created: 2008-02-19 Last updated: 2017-12-14Bibliographically approved
4. Comprehensive two-dimensional gas chromatography of the 209 polychlorinated biphenyls
Open this publication in new window or tab >>Comprehensive two-dimensional gas chromatography of the 209 polychlorinated biphenyls
2003 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, 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.

Keyword
Gas chromatography, comprehensive two-dimensional, Baltic grey seal, Polychlorinated biphenyls, Aroclors
Identifiers
urn:nbn:se:umu:diva-9222 (URN)10.1016/j.chroma.2003.08.100 (DOI)14650609 (PubMedID)
Available from: 2008-03-12 Created: 2008-03-12 Last updated: 2017-12-14Bibliographically approved
5. Comprehensive two-dimensional gas chromatography (GC x GC) of atropisomeric PCBs, combining a narrow bore beta-cyclodextrin column and a liquid crystal column
Open this publication in new window or tab >>Comprehensive two-dimensional gas chromatography (GC x GC) of atropisomeric PCBs, combining a narrow bore beta-cyclodextrin column and a liquid crystal column
2001 (English)In: Journal of Microcolumn Separations, ISSN 1040-7685, E-ISSN 1520-667X, Vol. 13, no 7, 300-305 p.Article in journal (Refereed) Published
Abstract [en]

Peak assignment and quantification of PCBs in environmental samples is a time-consuming and costly process, and the analysis of atropisomeric PCBs is even more laborious and costly due to the elaborate analytical work involved. GC X GC can solve some of the problems entailed by increasing congener resolution and instrument sensitivity. In this study. a comprehensive two-dimensional gas chromatography (GC X GC) system was utilized with a combination of a permethylated beta -cyclodextrin column in the first dimension and a liquid crystal column in the second dimension. Using this system, in a single GC X GC run six out of nine studied atropisomeric PCBs (PCBs 91, 132, 135. 136, 149, and 176) can be resolved, and two (PCBs 84 and 174) can be partially separated from coeluting congeners in a mixture of 144 congeners (the most abundant congeners in technical PCBs). The chiral resolution (Rs) of the enantiomeric pairs ranged between 0.6 and 2.0, with PCB 132 having the highest resolution. Furthermore, the congers that (partially) coelute with enantiomers of PCBs 84, 95, and 174 have low abundance in technical PCB as well as in environmental samples. Thus, all of the nine target PCBs could be separated from significant interfering compounds in a single GC X GC run.

Keyword
polychlorinated biphenyls, PCB, atropisomers, chiral analysis, comprehensive two-dimensional gas chromatography, beta-cyclodextrin, liquid crystal
Identifiers
urn:nbn:se:umu:diva-8878 (URN)10.1002/mcs.10010 (DOI)
Available from: 2008-02-19 Created: 2008-02-19 Last updated: 2017-12-14Bibliographically approved
6. Determination of atropisomeric and planar polychlorinated biphenyls, their enantiomeric fractions and tissue distribution in grey seals using comprehensive 2D gas chromatography
Open this publication in new window or tab >>Determination of atropisomeric and planar polychlorinated biphenyls, their enantiomeric fractions and tissue distribution in grey seals using comprehensive 2D gas chromatography
Show others...
2003 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1019, no 1-2, 127-142 p.Article in journal (Refereed) Published
Abstract [en]

High prevalence of uterine occlusions and sterility is found among Baltic ringed and grey seal. Polychlorinated biphenyls (CBs) are suspected to be the main cause. The CB concentrations are higher in affected than in healthy animals, but the natural variation is considerable. Thus, it might be possible to assess the health status of seals by CB analysis. The ratios of chiral compounds (enantiomeric fractions (EFs)) such as atropisomeric CBs are of particular interest, since these may reflect differences in metabolic rates. An analytical procedure was developed and used to determine the levels of atropisomeric CBs, planar-CBs (WHO-PCBs) and total CBs in seals of different health status. Comprehensive 2D gas chromatography (GC×GC) was used to separate the target analytes from other CBs and interferences and a micro electron-capture detector (μECD) was used for detection. EFs of the atropisomeric CBs were difficult to determine as the levels were low and the interferences many. Two column combinations had to be used to avoid biased results—both had a chiral column as first-dimension column. The second-dimension column was coated with either a high-polarity cyanopropyl or a liquid crystal phase. EFs were determined for five atropisomeric CBs, i.e. CBs 91, 95, 132, 149 and 174. The results were verified by GC×GC–time-of-flight mass spectrometry (TOF-MS). Some atropisomeric CBs had EFs that deviated strongly from the racemic-mixture value. The deviations were larger in liver than blubber, which indicates enantioselective metabolism. However, there was no selective passage of the studied atropisomeric CBs across placenta and no selective blood–brain barrier. Similarly, no correlation between EFs and health status was observed, although there was a correlation between the total CB levels and health status.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2003
Keyword
gas chromatography, comprehensive two-dimensional, atropisomers, enantiomeric fractions, Baltic grey seal, polychlormated biphenyls
National Category
Biochemistry and Molecular Biology Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-4603 (URN)10.1016/j.chroma.2003.08.102 (DOI)000186503600012 ()
Note

Publicerad som manuskript i avhandling med titel:

Determination of levels, enantiomeric fractions and tissue distribution of atropisomeric PCBs in grey seals (Halichoreus Grypus) of varying health status using comprehensive twodimensional gas chromatography

Available from: 2003-06-06 Created: 2003-06-06 Last updated: 2017-05-26Bibliographically approved

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Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
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  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
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  • text
  • asciidoc
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