Development of chemiluminescent ELISAs to DDT and its metabolites in food and environmental samples

Two enzyme-linked immunosorbent assays (ELISA) with chemiluminescent (CL) detection for the insecticide DDT and the group of DDT-related compounds have been optimized and characterized. Both conjugate-coated ELISAs are based on monoclonal antibodies (MAbs) of different specificity and homologous protein conjugates. Effects of several physicochemical factors (ionic strength, pH, Tween-20 and Bovine serum albumin (BSA) concentrations) and solvents (methanol, ethanol, acetone and N,N'-dimethylformamide) on the performance of the assays were studied and optimized. For the DDT-selective assay, the sensitivity, estimated as the I-50 value, was 0.6 mug/l, with a linear working range between 0.1 and 2 mug/l and a limit of detection of 0.06 mug/l. For the DDT group-selective assay, the sensitivity was 0.2 mug/l, with a linear working range between 0.07 and 1 mug/l and a limit of detection of 0.04 mug/l. CL-ELISAs were four times more sensitive compared to colorimetric ELISAs. Finally, both immunoassays were applied to the detection of DDT and group of DDT-related compounds in spiked real water, soil and food samples. (C) 2003 Elsevier B.V. All rights reserved.