Development of ELISA kit for the assay of ichlorodiphenyltrichloroethane in milk and milk products

Immunoassay of pesticide residues in foods is gaining importance in the past two decades. The objective of the present work is to develop an enzyme – linked immunosorbent assay (ELISA) kit for the assay of dichlorodiphenyltrichloroethane (DDT) in milk and milk products. Here, an ELISA method was developed using rabbit polyclonal antibodies against a hapten, DDT-OH for the detection of organochloride pesticide DDT in milk and milk products. The immunogen for raising the antiserum was prepared from BIS (4-chlorophenyl) ethanol and succinic anhydride coupled with bovine serum albumin (BSA) One ml of immunogen was inoculated subcutaneously in multiple sites of thigh region in rabbits following three boosters at weekly intervals and the antiserum was harvested after the second booster. The ELISA response of the anti DDT antiserum, diluted and undiluted was studied against the antigen (DDT) coated onto the immuno module. The homogenous response of the anti DDT anti serum was adequate to identify DDT. Fifteen samples each of milk, buttermilk, cheese, kalakhand and khoa were quantitatively analyzed for DDT using ELISA as well as GC methods. DDT was present only below detectable limit (BDL) (5 ng g-1) in milk and milk products obtained from organized dairies in and around Chennai city, India. The percentage recovery was above 70% ensuring that the ELISA method developed for DDT is dependable. The developed ELISA method can be helpful in detecting the residual amount of DDT present in milk and milk products. The analysis of pesticides in samples by ELISA and GC was comparable.