Development of a non-competitive immunoassay for monitoring DDT, its metabolites and analogues in water samples

This report highlights the characteristics of a general method of performing non-competitive immunoassays for low-molecular-mass analytes, which was developed and applied to 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) determination in aqueous samples. The method is based on the separation of the analyte-bound antibody from the excess of the free antibody by a chromatographic step, followed by the dissociation of the complex and the capture of the previously bound antibody on a solid phase. The measured signal is linearly correlated to the concentration of the complex and, consequently, to the analyte concentration. The 3sigma limit of detection (LOD, 8 ng l(-1)) obtained by the above method enabled us to decidedly improve the sensitivity of the corresponding enzyme-linked immunosorbant assay (ELISA) and of all reported immunoassays for DDT. In addition, by applying this new format, even if a very selective antibody was used, a broad selectivity was observed, which allowed DDT + DDD + DDE to be determined instead of only p,p'-DDT as in the ELISA performed with the same antibody. In addition, real water samples were validated in a percentage recovery test. Very good recovery rates were obtained, highlighting the validity of the proposed method to accurately determine the total DDT content in water. (C) 2003 Elsevier B.V. All rights reserved.