subsequent investigations, Ellerichmann showed that another chiral component of
the standard mixture, presumably 4-MeSO 2 -2,2
0 ,3,3
0 ,6-penta-CB (i.e. 4–84)
coeluted with the 3–91 peak, thus giving rise to a misinterpretation of the original
data set (Ellerichmann 2000). In general, in these early separation methods, the
MeSO 2 -PCBs exerted strong interactions with the chiral cyclodextrin phase and due
to the rather low maximum temperature for the column (468 K), the retention times
were long (from 50 min for 3–91 to 130 min for 4–174) despite the short length of
the column. The peak width at half height was 30 s for the MeSO 2 -pentaCBs and
increased to up to 110 s for the MeSO 2 -heptaCBs. Baseline separation was observed
for most enantiomers and constitutional isomers (Fig. 8.24).
Today’s optimised separation methods combining polysiloxane-based, highly
temperature stable phases with a minor proportion of CSP allow shorter retention
times and higher detection limits due to low column bleeding effects and combinations with highly sensitive detection methods (Sandala et al. 2004; Perez-Fernandez
et al. 2012; Quinete et al. 2014; Tang et al. 2016).
Peres-Fernandez et al. applied multidimensional heart-cut gas chromatography
coupled to a mass-selective detector for extending the separation capacity of
enantiomer-selective analysis of methyl sulfone PCBs in environmental samples
(Perez-Fernandez et al. 2012). The separation capacity of three β-CD-based capillary
columns (i.e. Chirasil-Dex, BGB-172 and BGB-176SE) was tested for the simultaneous enantiomeric separation of both polychlorinated biphenyls (PCBs) and
methylsulfonyl metabolites of PCBs (MeSO 2 -PCBs). The BGB-176SE capillary
column provided the best results, allowing the simultaneous enantioselective resolution of six MeSO 2 -PCBs and six chiral PCBs; the Chirasil-Dex column did not
resolve any of the studied MeSO 2 -PCBs; and a poor resolution was obtained for
three MeSO 2 -PCBs with the BGB-172 column. The developed method was successfully applied to two fish oil and one cow liver samples, which showed a different
enantioselective pattern. PCBs 91 and 176 presented a clear enrichment of the
second eluted atropisomer in codfish oil, whereas in fish oil samples, slight enrichment of the first eluted atropisomer of CB45 and the second eluted atropisomer of
CB136 was observed (Perez-Fernandez et al. 2012).
As a part of a human tissue screening, study six human livers and two human liver
were obtained from the “Institut für Rechtsmedizin at the University of Hamburg”
who performed an autopsy of seven persons, who had passed away due to heart
failure or accidents (Ellerichmann et al. 1998a, b, c). The liver samples were
analysed for the content as well as for the enantiomeric excess of the eight
MeSO 2 -PCBs mentioned above. Two MeSO 2 -PCBs (3–149 and 3–132) were
detected in all liver samples by gas chromatography and electron capture detection
(ECD), using an achiral column (NE 54), where for one sample cGC/MS full scan
analysis was applied (Ellerichmann et al. 1998a, b, c). The enantioselective gas
chromatographic analysis of tissue sample extracts with an ECD was not successful
due to interferences with the complex liver-matrix resulting in negative peaks in the
chromatograms. Attempts to remove these interferences failed. The matrix problems
were overcome by application of cGC/MS in electron ionisation mode and selected
8.2 Transformation/Accumulation of Chiral Xenobiotics in Higher Organisms
181
the standard mixture, presumably 4-MeSO 2 -2,2
0 ,3,3
0 ,6-penta-CB (i.e. 4–84)
coeluted with the 3–91 peak, thus giving rise to a misinterpretation of the original
data set (Ellerichmann 2000). In general, in these early separation methods, the
MeSO 2 -PCBs exerted strong interactions with the chiral cyclodextrin phase and due
to the rather low maximum temperature for the column (468 K), the retention times
were long (from 50 min for 3–91 to 130 min for 4–174) despite the short length of
the column. The peak width at half height was 30 s for the MeSO 2 -pentaCBs and
increased to up to 110 s for the MeSO 2 -heptaCBs. Baseline separation was observed
for most enantiomers and constitutional isomers (Fig. 8.24).
Today’s optimised separation methods combining polysiloxane-based, highly
temperature stable phases with a minor proportion of CSP allow shorter retention
times and higher detection limits due to low column bleeding effects and combinations with highly sensitive detection methods (Sandala et al. 2004; Perez-Fernandez
et al. 2012; Quinete et al. 2014; Tang et al. 2016).
Peres-Fernandez et al. applied multidimensional heart-cut gas chromatography
coupled to a mass-selective detector for extending the separation capacity of
enantiomer-selective analysis of methyl sulfone PCBs in environmental samples
(Perez-Fernandez et al. 2012). The separation capacity of three β-CD-based capillary
columns (i.e. Chirasil-Dex, BGB-172 and BGB-176SE) was tested for the simultaneous enantiomeric separation of both polychlorinated biphenyls (PCBs) and
methylsulfonyl metabolites of PCBs (MeSO 2 -PCBs). The BGB-176SE capillary
column provided the best results, allowing the simultaneous enantioselective resolution of six MeSO 2 -PCBs and six chiral PCBs; the Chirasil-Dex column did not
resolve any of the studied MeSO 2 -PCBs; and a poor resolution was obtained for
three MeSO 2 -PCBs with the BGB-172 column. The developed method was successfully applied to two fish oil and one cow liver samples, which showed a different
enantioselective pattern. PCBs 91 and 176 presented a clear enrichment of the
second eluted atropisomer in codfish oil, whereas in fish oil samples, slight enrichment of the first eluted atropisomer of CB45 and the second eluted atropisomer of
CB136 was observed (Perez-Fernandez et al. 2012).
As a part of a human tissue screening, study six human livers and two human liver
were obtained from the “Institut für Rechtsmedizin at the University of Hamburg”
who performed an autopsy of seven persons, who had passed away due to heart
failure or accidents (Ellerichmann et al. 1998a, b, c). The liver samples were
analysed for the content as well as for the enantiomeric excess of the eight
MeSO 2 -PCBs mentioned above. Two MeSO 2 -PCBs (3–149 and 3–132) were
detected in all liver samples by gas chromatography and electron capture detection
(ECD), using an achiral column (NE 54), where for one sample cGC/MS full scan
analysis was applied (Ellerichmann et al. 1998a, b, c). The enantioselective gas
chromatographic analysis of tissue sample extracts with an ECD was not successful
due to interferences with the complex liver-matrix resulting in negative peaks in the
chromatograms. Attempts to remove these interferences failed. The matrix problems
were overcome by application of cGC/MS in electron ionisation mode and selected
8.2 Transformation/Accumulation of Chiral Xenobiotics in Higher Organisms
181