Lipophilicity cyclodienes

Lindane is one of eight different hexachlorocyclohexane (HCH), C H Cl, isomers and its Chemical Abstract n.2cniQ is la, 2a 3P, 4a, 5a 6P-hexachlorocyclohexane [58-89-9] (y-HCH or y-BHC, ben2ene hexachloride) (80). Commercial products containing lindane are marketed as either a mixture of isomers or as the pure y-BHC isomer. Not unexpectedly, lindane is a highly stable lipophilic compound and it has been used extensively worldwide as an insecticide. In contrast, hexachloropentadiene, C Cl, is an extremely reactive industrial intermediate used as a chemical intermediate in the synthesis of a broad range of cyclodiene-derived pesticides, which include endosulfan, endrin, heptachlor, and several different organohalogen flame retardants (81). 

In terrestrial animals, cyclodienes such as dieldrin, like other refractive lipophilic pollutants, can be excreted in their unchanged forms, notably with lipoproteins, which are exported into milk (mammals), eggs (birds, reptiles, insects), or developing... 

In classical structure-activity studies, most of the attempts concentrated on correlating the activity with one of the molecular properties— e.g., the carcinogenic activity of polynuclear aromatic compounds with their electronic structure (18, 19), the narcotic activity with lipophilicity 20, 21), the insecticidal activity of cyclodienes with their three-dimensional molecular silhouette 22), etc. Sometimes the activity correlated well with only one of the molecuar parameters. In our approach these are special cases where other physicochemical properties do not play critical roles in determining the variation in the activity within a set of congeners so that the coefficients defining these other properties are zero. 

Their presence in these products is not surprising since as a group the cyclodienes are apolar, lipophilic compounds. Acceptable daily intake for cyclodienes has been established by the World Health Organization and tolerance limits in meats and poultry set by the US-EPA. Development of an immunoassay for these compounds would greatly facilitate improved monitoring for cyciodienes in foods and environmental samples. We have isolated a monoclonal antibody, LLNL-Hept-2. that detects cyclodiene insecticides and have used this antibody to develop an immunoassay that is able to detect heptachlor (and related chlorinated cyciodienes) in meat, flsh and dairy products. 

Our results clearly point out the critical role of sample cleanup in development of an immunoassay for lipophilic compounds. The methods should be simple, rapid, and capable of being exported into the field if the full potential of immunoassays are to be realized. The sample cleanup method we describe here meets these criteria for heptachlor, aldrin and chlordane. However, recovery experiments clearly indicate that the more polar epoxides of these insecticides are retained on the column. Thus, while the antibody binds all cyclodiene insecticides with roughly equal affinity, the cleanup method will not equally present the cyclodienes to the assay. Attempts at using mixed solvent elution systems such as ether/hexane remove the more polar insecticides but also remove more of the starting fat and interfering compound(s). Thus, further efforts in the area of sample cleanup are needed. 

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