Toxaphene single components

In 1973, variant (i) was introduced by Khalifa et al. and the year after three reports were published which described the isolation and structure elucidation of single components from technical toxaphene [54, 78, 91]. These initial studies focused on the isolation and structure elucidation of the major components in the technical mixture. However, it turned out that the isolated components were easily degraded in biota. Nevertheless, this approach revealed interesting results such as the presence of dihydrocamphenes in toxaphene [43,44] and the isolation of a non-racemic component from the technical product Melipax [27]. 

The aim of variant (iii) is to obtain well-defined low-chlorinated single toxaphene components. Further chlorination of the single components allows one to produce several higher chlorinated components. The idea of this approach goes back to the initial investigators of the mechanisms of camphene chlorination [38,39,46]. In 1976, Parlar et al. prepared seven low-chlorinated bornanes by adding small amounts of Cl2 to camphene [103]. In a similar way, Turner et al. isolated 2-exo,10-dichlorobornane (B2-20). Photochlorination of B2-20 resulted in B7-515 (P-32) [53]. Parlar and co-workers applied this method to pro-... 

The bulk of the toxaphene components detected in environmental samples are polychlorinated bornanes and a few camphenes or bornenes. Since reductive dechlorination of polychlorinated bornanes leads to bornanes with one less chlorine atom, at present it is not possible to distinguish unequivocally between components originating from technical toxaphene and dechlorinated metabolites. This question can only be solved with fate studies of single components in the laboratory [122,165],... 

The scientific interest in toxaphene has increased significantly during the past five years as can be seen from the increasing number of papers registered in the Chemical Abstracts Services. The availability of single standard components is probably one of the major reasons for this. Therefore, the following chapters focus mainly on a critical discussion of congener-specific analysis techniques. 

Before the introduction of gas chromatography, the detection of toxaphene was carried out mainly by infrared spectroscopy [57, 58], measurement of total chloride content [59], or colorimetric methods [60]. Colorimetric methods had a detection limit around 100 pg/mL [60]. Coulson et al. pubhshed the first gas chromatogram of toxaphene in 1959 which clearly demonstrates the problem of the analysis of toxaphene. Due to the high number of components no signals of single compounds were observable in contrast to the case for other chloro-pesticides such as DDT, lindane, and chlordane [61]. 

Compounds with a sufficient volatility and thermal stability can be ionized in the vapor phase by bombardment with high-energy electrons which removes electrons from occupied orbitals [107]. According to our search of the literature, the first mass spectrometric analysis of toxaphene was reported in 1966 [108], and the first GC/EI-MS of a single toxaphene was published in 1974 [62]. Nowadays, numerous references are available containing many mass spectra and detailed descriptions of the EI-MS-fragmentations of polychlorinated bornanes [109-116]. Here, only the basic approach is given for the interpretation of El-MS. Most El-MS of polychlorinated bornanes lack the molecular ion in contrast to toxaphene components with one or two double bonds where it is clearly visible [109]. 

More recent studies preferred injector temperatures of below 200°C to avoid decomposition in the splitless injector [146]. However, low injector temperatures increase the risk of an incomplete transfer of the sample onto the GC column. To overcome this problem, a pressure-pulsed injection has been suggested [125, 157-159]. Detailed investigations with single toxaphene components have shown that the response factors of less volatile components can be increased fourfold by this technique using an injector temperature of 230°C (see Fig. 9 for an example) [158,159],... 

Figure 9 also demonstrates clearly that the detector responses of single toxaphene components are different [95], However, due to thermodegradation they might also be influenced by the injection method [76,94]. 

Environmental Fate and Toxicology of Single Toxaphene Components... 

Few data about toxaphene levels in human adipose tissue were found in a search of the literature carried out in 1991 [197], i.e., before the introduction of single toxaphene standards. Gill et al. carried out two studies about levels in human blood and serum [198,199]. The congener-specific analysis was performed with on-column injection on a 25 m long DB-5 capillary and NICI-MS detection. In the first study nine octachloro- or nonachlorobornanes were detected. B8-1413 (P-26) and B9-1679 (P-50) were the most abundant congeners [198]. Using the 22-component standard, B8-1414 (P-40) or B8-1945 (P-41) and B8-2229 (P-44) were also identified as abundant peaks [199]. B8-1413 (P-26) and B9-1679 (P-50) are... 

First toxicological studies with single toxaphene components were carried out in the 1970s to find important relations between structure and toxicity [244]. At that time, the toxic potential of components isolated from technical toxaphene was investigated. The compounds B7-515 (P-32 or Toxicant B) and B8-806/9 (P-42 or Toxicant A) were tested concerning their acute toxicity for fish, rats and insects. 

First toxicological studies with single toxaphene components were performed. 

---