with cGC on a Chirasil-DEX column. Beside this investigation, bromocyclen was
included in various surveys and monitoring programs applying non-stereoselective
quantitative analytical methods (Li et al. 2014; Hildmann et al. 2015; Perugini et al.
2018).
Toxaphene
® is a broad-range pesticide produced in the US, which was used
primarily on cotton and soya bean in the south-eastern United States. Similar
products were produced under the brandname Melipax
® (Germany) and
Polychloropinene
® (former Soviet Union). For simplification reasons, in the following section, single compounds associated with these pesticide mixtures will only be
called Toxaphene
® congeners (de Geus et al. 1999, 2000). Toxaphene
® use was
banned by the US Environmental Protection Agency in 1986 because of its persistence and environmental toxicity. However, residues of technical toxaphene are still
found in biota far removed from sites of its former application. Technical toxaphene
is synthesised by the exhaustive chlorination of camphene, whereas the former
Sowjet product Polychloropinene
® used natural α-pinene as starting material
(Shinova 1974; Trukhin et al. 2007), followed by a Wagner-Meerwein
rearrangement taking place under the usual experimental conditions, thus giving
rise to the formation of polychlorinated 1,7,7-trimethyl-bicyclo[2,2,1]heptanes
(bornanes). Theoretically, 32767 chlorinated bornanes are conceivable, 16128 of
which exist as enantiomeric pairs, while only 511 are achiral (Vetter and Schurig
1997). As a consequence, Toxaphene
® (and other brands) is an extremely complex
mixture of hexa- to decachlorinated bornanes, bornenes, camphenes and
camphedienes. In technical mixtures, only selected congeners have been detected
thus far (Fig. 8.19). The nomenclature of this class of compounds is however
unsatisfactory, because the IUPAC names are very long and can hardly be used in
a manuscript for scientific publications. Therefore, several suggestions for acronyms
and alternative nomenclatures were made for more convenient applications, two of
which seem to dominate, that is, the Palar numbers (Coelhan and Parlar 1996) and
the systematic code names proposed by Andrews and Vetter (1995). These will also
be used in the present monograph (Table 8.13). In addition, suggestions by Oehme
and Kallenborn (1995), and by Nikiforov et al. (1995) are worth mentioning. As few
of its numerous congeners have been synthesised thus far, toxaphene congeners can
only be separated and analysed effectively with a highly selective analytical technique. In addition to the large number of congeners, the following problems have to
be overcome: First, gas chromatographic enantiomer separation of toxaphene congeners requires relatively high temperatures, which turned out to be unfavourable to
a good chromatographic performance (Coelhan and Parlar 1996; Vetter and Schurig
1997). Second, Buser and Müller (1994a, b) presented experimental evidence that
non-racemic congeners may be present in technical mixtures of toxaphenes. At first,
these reports caused some scepticism among the scientists. However, recently Vetter
et al. were able to isolate the heptachlorobornane B7-1453 from the technical
product Melipax (produced in the former German Democratic Republic), which
showed different peak abundance of the enantiomers (ER ¼ 1.26 Æ 0.03). Furthermore, the authors excluded interferences and co-elution with another compound.
Therefore, they conclude that B7-1453 and possibly other chlorobornanes are
8.2 Transformation/Accumulation of Chiral Xenobiotics in Higher Organisms
159
included in various surveys and monitoring programs applying non-stereoselective
quantitative analytical methods (Li et al. 2014; Hildmann et al. 2015; Perugini et al.
2018).
Toxaphene
® is a broad-range pesticide produced in the US, which was used
primarily on cotton and soya bean in the south-eastern United States. Similar
products were produced under the brandname Melipax
® (Germany) and
Polychloropinene
® (former Soviet Union). For simplification reasons, in the following section, single compounds associated with these pesticide mixtures will only be
called Toxaphene
® congeners (de Geus et al. 1999, 2000). Toxaphene
® use was
banned by the US Environmental Protection Agency in 1986 because of its persistence and environmental toxicity. However, residues of technical toxaphene are still
found in biota far removed from sites of its former application. Technical toxaphene
is synthesised by the exhaustive chlorination of camphene, whereas the former
Sowjet product Polychloropinene
® used natural α-pinene as starting material
(Shinova 1974; Trukhin et al. 2007), followed by a Wagner-Meerwein
rearrangement taking place under the usual experimental conditions, thus giving
rise to the formation of polychlorinated 1,7,7-trimethyl-bicyclo[2,2,1]heptanes
(bornanes). Theoretically, 32767 chlorinated bornanes are conceivable, 16128 of
which exist as enantiomeric pairs, while only 511 are achiral (Vetter and Schurig
1997). As a consequence, Toxaphene
® (and other brands) is an extremely complex
mixture of hexa- to decachlorinated bornanes, bornenes, camphenes and
camphedienes. In technical mixtures, only selected congeners have been detected
thus far (Fig. 8.19). The nomenclature of this class of compounds is however
unsatisfactory, because the IUPAC names are very long and can hardly be used in
a manuscript for scientific publications. Therefore, several suggestions for acronyms
and alternative nomenclatures were made for more convenient applications, two of
which seem to dominate, that is, the Palar numbers (Coelhan and Parlar 1996) and
the systematic code names proposed by Andrews and Vetter (1995). These will also
be used in the present monograph (Table 8.13). In addition, suggestions by Oehme
and Kallenborn (1995), and by Nikiforov et al. (1995) are worth mentioning. As few
of its numerous congeners have been synthesised thus far, toxaphene congeners can
only be separated and analysed effectively with a highly selective analytical technique. In addition to the large number of congeners, the following problems have to
be overcome: First, gas chromatographic enantiomer separation of toxaphene congeners requires relatively high temperatures, which turned out to be unfavourable to
a good chromatographic performance (Coelhan and Parlar 1996; Vetter and Schurig
1997). Second, Buser and Müller (1994a, b) presented experimental evidence that
non-racemic congeners may be present in technical mixtures of toxaphenes. At first,
these reports caused some scepticism among the scientists. However, recently Vetter
et al. were able to isolate the heptachlorobornane B7-1453 from the technical
product Melipax (produced in the former German Democratic Republic), which
showed different peak abundance of the enantiomers (ER ¼ 1.26 Æ 0.03). Furthermore, the authors excluded interferences and co-elution with another compound.
Therefore, they conclude that B7-1453 and possibly other chlorobornanes are
8.2 Transformation/Accumulation of Chiral Xenobiotics in Higher Organisms
159