Development of Elisa Kit for the Assay of Dichlorodiphenyltrichloroethane in Milk and Milk Products and Comparision with Gas Chromatography

Organochlorine pesticides like DDT are highly persistent and tend to accumulate in the body fat and
subsequently excreted in milk. Immunoassay of pesticide residues in foods is gaining importance in
recent past years. With the objective of developing an enzyme – linked immunosorbent assay (ELISA)
kit for the assay of dichlorodiphenyltrichloroethane (DDT) in milk and milk products, 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 anti serum (diluted and undiluted) was studied
against the antigen (DDT) coated onto the immune-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. The
analysis of pesticides in samples by ELISA and GC was comparable. 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, Tamil Nadu. The ELISA method developed for DDT is dependable, as the
percentage recovery was above 70 per cent. The developed ELISA method can be helpful in
detecting even the residual amount of DDT present in milk and milk products.