samples of rainbow trout with this new environmental pollutant (Rimkus and Wolf
1992). This was at that time a surprising result, as there is no official registration of
this substance for fish farming.
The appearance of this new environmental contaminant triggered two follow-up
studies by Pfaffenberger et al. (1994a, b) and by Bethan et al. (1996, 1997).
Pfaffenberger et al. analysed fish samples from various fish farms in Denmark and
from the river Stör, a tributary of the Elberiver in the northern German state
Schleswig-Holstein. They focused on the problem as to whether a significant
enzymatic transformation of bromocyclen is possible at that trophic level. Particular
emphasis was placed upon the question of whether a correlation between the
concentration of bromocyclen and its enantiomeric ratio can be inferred from
enantioselective cGC using modified cyclodextrins as chiral selector.
The fish samples were collected during the spring of 1990 and the autumn of
1992. The rainbow trouts (Oncorhynchus mykiss (WAL.)) were imported from
various fish farms in Denmark. The other fish species orfe (Leuciscus idus L.),
bream (Abramisbrama orientalis BERG) and pike (Esox lucius (L.)) were caught
in the river Stör. Sample preparation and clean-up can be found in the here-discussed
report (Pfaffenberger et al. 1994a, b). In all eight fish samples, in part, remarkably
high concentrations of bromocyclen were determined. They varied between 0.093
and 1.200 mg/kg, regardless of whether the fishes lived in the artificial environment
of a fish farm or in a natural riverine environment like the river Stör. Furthermore, no
correlation between the fish species and the observed concentrations were found.
With regard to the determination of enantiomeric excesses, Pfaffenberger et al.
were the first to separate the enantiomers of bromocyclen in fish tissue extracts. An
example of these first successful enantiomer separations with the help of a 25-m
fused-silica capillary column, coated with 50% (w/w) heptakis(6-Otertbutyldimethylsilyl-2,3-di-O-methyl)-β-cyclodextrin and 50% OV-1701, is
shown in Fig. 8.16. The enantiomeric ratios as determined in the fish samples are
summarised in Table 8.11. The ERs vary between 0.84 and 1.00. In all samples of
the different fish species, the first eluting (À)-enantiomer was preferentially
transformed, with the exception of one sample which showed an ER of 1.00 (the
assignment of the order of elution of enantiomers is based on optical rotation
measurements after enantiomeric resolution by preparative packed-column GC
(König et al. 1994a, b, c)). This effect was observed regardless of whether the
sample originated from fish farms or from the river Stör. Therefore, it can be safely
assumed that an enzymatic process, which is common to all fish species investigated
by Pfaffenberger et al., gave rise to the enantioselective transformation of
bromocyclen. As for the samples from a fish farm, a correlation between the
enantiomeric ratios and the concentration can be inferred (Fig. 8.17). However,
caution has to be applied when interpreting this result from a statistical point of
view. The observed correlation is based on a consistent but small data set, and it is,
therefore, not statistically significant. However, the observed enantiomeric ratios in
the fish samples imply that at least the (À)-enantiomer can be metabolised to some
degree.
The source of contamination which led to the high concentration in this matrix
was unclear. It could not be excluded that effluents of municipal sewage treatment
156
8 Enantiomer-Specific Fate and Behaviour of Chiral Contaminants
1992). This was at that time a surprising result, as there is no official registration of
this substance for fish farming.
The appearance of this new environmental contaminant triggered two follow-up
studies by Pfaffenberger et al. (1994a, b) and by Bethan et al. (1996, 1997).
Pfaffenberger et al. analysed fish samples from various fish farms in Denmark and
from the river Stör, a tributary of the Elberiver in the northern German state
Schleswig-Holstein. They focused on the problem as to whether a significant
enzymatic transformation of bromocyclen is possible at that trophic level. Particular
emphasis was placed upon the question of whether a correlation between the
concentration of bromocyclen and its enantiomeric ratio can be inferred from
enantioselective cGC using modified cyclodextrins as chiral selector.
The fish samples were collected during the spring of 1990 and the autumn of
1992. The rainbow trouts (Oncorhynchus mykiss (WAL.)) were imported from
various fish farms in Denmark. The other fish species orfe (Leuciscus idus L.),
bream (Abramisbrama orientalis BERG) and pike (Esox lucius (L.)) were caught
in the river Stör. Sample preparation and clean-up can be found in the here-discussed
report (Pfaffenberger et al. 1994a, b). In all eight fish samples, in part, remarkably
high concentrations of bromocyclen were determined. They varied between 0.093
and 1.200 mg/kg, regardless of whether the fishes lived in the artificial environment
of a fish farm or in a natural riverine environment like the river Stör. Furthermore, no
correlation between the fish species and the observed concentrations were found.
With regard to the determination of enantiomeric excesses, Pfaffenberger et al.
were the first to separate the enantiomers of bromocyclen in fish tissue extracts. An
example of these first successful enantiomer separations with the help of a 25-m
fused-silica capillary column, coated with 50% (w/w) heptakis(6-Otertbutyldimethylsilyl-2,3-di-O-methyl)-β-cyclodextrin and 50% OV-1701, is
shown in Fig. 8.16. The enantiomeric ratios as determined in the fish samples are
summarised in Table 8.11. The ERs vary between 0.84 and 1.00. In all samples of
the different fish species, the first eluting (À)-enantiomer was preferentially
transformed, with the exception of one sample which showed an ER of 1.00 (the
assignment of the order of elution of enantiomers is based on optical rotation
measurements after enantiomeric resolution by preparative packed-column GC
(König et al. 1994a, b, c)). This effect was observed regardless of whether the
sample originated from fish farms or from the river Stör. Therefore, it can be safely
assumed that an enzymatic process, which is common to all fish species investigated
by Pfaffenberger et al., gave rise to the enantioselective transformation of
bromocyclen. As for the samples from a fish farm, a correlation between the
enantiomeric ratios and the concentration can be inferred (Fig. 8.17). However,
caution has to be applied when interpreting this result from a statistical point of
view. The observed correlation is based on a consistent but small data set, and it is,
therefore, not statistically significant. However, the observed enantiomeric ratios in
the fish samples imply that at least the (À)-enantiomer can be metabolised to some
degree.
The source of contamination which led to the high concentration in this matrix
was unclear. It could not be excluded that effluents of municipal sewage treatment
156
8 Enantiomer-Specific Fate and Behaviour of Chiral Contaminants