HAPTEN SYNTHESIS AND DEVELOPMENT OF ELISAS FOR DETECTION OF ENDOSULFAN IN WATER AND SOIL

Two enzyme immunoassays, a laboratory assay based on microwell plates and a field test based on the use of small polystyrene tubes, have been developed for the detection of endosulfan (1,4,5,6,7,7-hexachloro-8,9,10-trinorborn-5-en-2,3-ylenedimethyl sulfite) residues in water and soil. To raise antibodies that are sensitive and selective for the toxic forms of endosulfan, three haptens were prepared. One hapten was prepared by derivatization of endosulfan diol [1,4,5,6,7,7-hexachloro-2,3-bis(hydroxymethyl)norborn-5-ene], while the others used derivatives of a rigid five-membered ring adjacent to the bridged hexachlorocyclopentadiene (cyclodiene) ring. Different hapten combinations were used for immunogen and reporter enzyme conjugate in both the microwell and field assays. The optimized assays have detection limits of about 0.2 ppb endosulfan and detect in the range 0.2-10 ppb (0.2-20 ppb for field assay, without sample dilution). Water samples can be analyzed directly without solvent extraction or concentration, while soil samples are simply extracted with 90% methanol. The tests detect endosulfan sulfate (1,4,5,6,7,7-hexachloro-8,9,10-trinorborn-5-en-2,3-ylenedimethyl sulfate) with sensitivity similar to that for endosulfan but-are 4-10 times less sensitive to endosulfan diol, and therefore the assays can potentially determine toxic compounds of endosulfan (endosulfan and endosulfan sulfate) from the total endosulfan residues present in the environment.