Broadening the antibody specificity by hapten design for an enzyme-linked immunoassay as an improved screening method for the determination of nitroaromatic residues in soils

The development of a group-specific immunochemical test as a new approach to screening is reported. The broadening of antibody specificity was achieved by design of the hapten part of the immunogen. We used molecular modelling to investigate the structure of the hapten and the influence of the spacer on its conformation and electronic nature as compared with the analyte thereby allowing a selection of suitable primary molecules for immunization. This offers the possibility of directing the cross-reactivity of the antibodies against structurally related compounds to a lower or a higher value. The analysis of 2,4,6-trinitrotoluene (TNT), its precursors and degradation products as residues in soils was performed in an enzyme-linked immunosorbent assay (ELISA). A polyclonal anti-dinitrotolyl antiserum (AB1) was compared with a polyclonal anti-trinitrophenyl antiserum (AB2). Both sera were found to be similar in relation to the detection limit (2 μg/1) and sensitivity but differ in their affinities to structurally related compounds. AB2 is selective to TNT. AB1 is able to recognize important structurally related compounds even at low concentrations. AB1 would be chosen to develop an immunochemical screening method. Real soil samples were investigated by ELISA and micellar electrokinetic capillary chromatography using the same extract solution. This combination could offer the possibility of rapid, cost efficient screening and determination of TNT and its degradation products.