cyclodextrin as a chiral stationary phase to the residual analysis of environmental
samples was applied for the first time in order to determine the enantiomeric profile
for α-HCH in marine surface waters. In a subsequent systematic investigation by
Faller et al. (1991a, b), 16 water samples representing all parts of the North Sea that
are interesting both from an oceanographic and chemical view were taken by means
of 10-L glass samplers. The sampler consists of an all-glass round flask (flat
100-mm-wide ground neck) that is fixed by a stainless-steel protective basket and
closed by a stainless-steel cover with two inlets for glass tubes which can be opened
in a predetermined depth. For further details, the reader should refer to the paper by
Gaul and Ziebarth (Gaul and Ziebarth 1983). In general, the sampling depth was
10 m. The water samples were extracted, purified and analysed according to known
procedures, which include extraction of 10 L of the respective seawater sample by
200 mL n-hexane, purification of the extract by column chromatography over an
pre-conditioned (2 h heated at 850
C and 5 vol. % H 2 O added) neutral alumina (¼
Al 2 O 3 ) column, and fractionation by normal-phase silica HPLC (Hühnerfuss et al.
1992a, b). Subsequently, the enantiomeric ratios for α-HCH were determined in the
purified fraction by applying enantiomer-selective cGC. The ER was directly
obtained by peak integration of the gas chromatogram and dividing the peak area
E 1 of the first eluting (+)-α-HCH through the peak area E 2 of the second-eluting (À)α-HCH enantiomer, that is, ER ¼ E 1 /E 2 . The results thus obtained revealed different
microbial transformation pathways in the North Sea (Fig. 8.5): while in the eastern
part of the North Sea including the German Bight and the Skagerrak, a preferential
reduction of the (+)-α-HCH was observed (ER ~ 0.85), and in the area east off the
coast of Great Britain, preferably (À)-α-HCH is the minor constituent (ER ~ 1.15).
This pattern indicates different region-specific microbial and enzymatic preferences in the water masses. A similar region-specific enantiomer distribution profile
was found in a circum-Arctic survey for the Arctic Ocean (Jantunen and Bidleman
1998). In this study, the enantiomeric profile for α-HCH was distinctly different
between the Western and Eastern Arctic waters. Enantioselective transformation of
(À)-α-HCH was found in the Bering and Chukchi seas, whereas the (+)-enantiomer
was depleted in the Arctic Ocean and the Greenland Sea. Thus, the evaluation of
enantiomeric profiles in water masses may contribute to the hydraulic and bathymetric water mass characterisation. Follow-up studies on related profiles on enantiomeric distribution in Arctic sediments and benthic Arctic food webs revealed a
complex and dynamic enantiomer-selective distribution process resulting in variable
enantiomeric distribution pathways within the Arctic environment (Hoekstra et al.
2003a, b, c; Borga and Bidleman 2005; Jin et al. 2017).
Hühnerfuss and co-workers (1992a, b) identified and provided the first overview
on the preferential transformation of (+)-α-HCH in the eastern part of the North Sea
analyses of additional water samples from the German Bight and from the Baltic Sea
(Hühnerfuss et al. 1992a, b). Furthermore, the main transformation products both of
α-HCH and γ-HCH, that is, β-PCCH and γ-PCCH, respectively, were for the first
time included in enantioselective analyses of marine water samples. The respective
gas chromatograms of these two HCH metabolites, extracted from Baltic Sea water
8.1 Microbial Transformation of Chiral Environmental Pollutants
119
samples was applied for the first time in order to determine the enantiomeric profile
for α-HCH in marine surface waters. In a subsequent systematic investigation by
Faller et al. (1991a, b), 16 water samples representing all parts of the North Sea that
are interesting both from an oceanographic and chemical view were taken by means
of 10-L glass samplers. The sampler consists of an all-glass round flask (flat
100-mm-wide ground neck) that is fixed by a stainless-steel protective basket and
closed by a stainless-steel cover with two inlets for glass tubes which can be opened
in a predetermined depth. For further details, the reader should refer to the paper by
Gaul and Ziebarth (Gaul and Ziebarth 1983). In general, the sampling depth was
10 m. The water samples were extracted, purified and analysed according to known
procedures, which include extraction of 10 L of the respective seawater sample by
200 mL n-hexane, purification of the extract by column chromatography over an
pre-conditioned (2 h heated at 850
C and 5 vol. % H 2 O added) neutral alumina (¼
Al 2 O 3 ) column, and fractionation by normal-phase silica HPLC (Hühnerfuss et al.
1992a, b). Subsequently, the enantiomeric ratios for α-HCH were determined in the
purified fraction by applying enantiomer-selective cGC. The ER was directly
obtained by peak integration of the gas chromatogram and dividing the peak area
E 1 of the first eluting (+)-α-HCH through the peak area E 2 of the second-eluting (À)α-HCH enantiomer, that is, ER ¼ E 1 /E 2 . The results thus obtained revealed different
microbial transformation pathways in the North Sea (Fig. 8.5): while in the eastern
part of the North Sea including the German Bight and the Skagerrak, a preferential
reduction of the (+)-α-HCH was observed (ER ~ 0.85), and in the area east off the
coast of Great Britain, preferably (À)-α-HCH is the minor constituent (ER ~ 1.15).
This pattern indicates different region-specific microbial and enzymatic preferences in the water masses. A similar region-specific enantiomer distribution profile
was found in a circum-Arctic survey for the Arctic Ocean (Jantunen and Bidleman
1998). In this study, the enantiomeric profile for α-HCH was distinctly different
between the Western and Eastern Arctic waters. Enantioselective transformation of
(À)-α-HCH was found in the Bering and Chukchi seas, whereas the (+)-enantiomer
was depleted in the Arctic Ocean and the Greenland Sea. Thus, the evaluation of
enantiomeric profiles in water masses may contribute to the hydraulic and bathymetric water mass characterisation. Follow-up studies on related profiles on enantiomeric distribution in Arctic sediments and benthic Arctic food webs revealed a
complex and dynamic enantiomer-selective distribution process resulting in variable
enantiomeric distribution pathways within the Arctic environment (Hoekstra et al.
2003a, b, c; Borga and Bidleman 2005; Jin et al. 2017).
Hühnerfuss and co-workers (1992a, b) identified and provided the first overview
on the preferential transformation of (+)-α-HCH in the eastern part of the North Sea
analyses of additional water samples from the German Bight and from the Baltic Sea
(Hühnerfuss et al. 1992a, b). Furthermore, the main transformation products both of
α-HCH and γ-HCH, that is, β-PCCH and γ-PCCH, respectively, were for the first
time included in enantioselective analyses of marine water samples. The respective
gas chromatograms of these two HCH metabolites, extracted from Baltic Sea water
8.1 Microbial Transformation of Chiral Environmental Pollutants
119