2- Chlorophenyl phosphorodi

Pioneering work on immunochemical assays for pesticides involved the synthesis of haptens for DDT and malathion. Haas and Guardia (24) used the acid chlorides of malathion half ester and DDA (2,2-bis-[j)-chlorophenyl]acetic acid) for conjugation while Centeno et al. (25) used the anhydrides of DDA and malathion diacid (0,0-dimethyl S-[l,2-bis-carboxyethyl]phosphorodi-thioate). In retrospect, more specific antibodies of a higher titer may have been obtained had a spacer arm been used. 

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