DEVELOPMENT OF A PANEL OF IMMUNOASSAYS FOR MONITORING DDT, ITS METABOLITES, AND ANALOGS IN FOOD AND ENVIRONMENTAL MATRICES

A panel of antisera was prepared using analogues and derivatives of me tabolites of the organochlorine insecticide, p,p'-DDT as haptens. The assays developed exhibited differing cross-reactions for different DDT analogues and metabolites, and the choice of hapten for the detecting enzyme conjugate had almost as much effect on assay specificity and s ensitivity as the structure of the hapten used for antibody production . Those assays developed using hapten I, based on esters of bis(p-chlo rophenyl)acetic acid (DDA), typically detected DDA with greater sensit ivity than p,p'-DDT or p,p'-DDE. The most sensitive assay for p,p'-DDT (lower limit of detection of 0.3 mu g/L) was obtained using an immuno gen based on bis(p-chlorophenyl)ethanol (hapten IV), although a signif icant crossreaction with dichlorodiphenyltrichloroethane (DDD) and DDE was obtained. The most specific assay for p,p'-DDT was obtained using an immunogen (hapten VI) that includes all elements of the DDT struct ure, except that one of the p-chloro groups was replaced by beta-alani ne carboxamide for coupling to carrier proteins. Antibodies based on a similar DDE hapten (V) exhibited specificity for p,p'-DDE over p,p'-D DT. Greater specificity and sensitivity for dicofol were obtained by u sing an immunogen derived from ester hydrolysis of chlorbenzilate (hap ten II). The assays provided methods for detection of p,p'-DDT plus p, p'-DDE either by using the antibody raised to hapten IV with conjugate based on hapten Ib or by using the assay based on hapten V, with trea tment of samples with warm alcoholic KOH, which converted DDT to DDE. Some of the immunoassays were applied to the detection of DDT and DDE in water, soil, and selected foods.