Development of homogeneous phase-modulation fluoroimmunoassay for 2,4-dichlorophenoxyacetic acid

This paper describes a homogeneous and competitive fluoroimmunoassay techni que using two methods of phase-modulation fluorescence spectroscopy in whic h non-labelled analyte, 2,4-dichlorophenoxyacetic acid (2,4-D), competes wi th the fluorescent-labelled antigen (2,4-D-NH2F) for non-labelled monoclona l antibody. In the first method the fluorescence lifetime difference betwee n the free and the monoclonal antibody-bound 2,4-D-NH2F is used to determin e both fractions by means of a phase-modulation mathematical approach. The second method is based on the simultaneous equation method using phase-reso lved fluorescence spectroscopy. The equation system generated is solved by the pseudo-inverse method. An analytical parameter comparison of the differ ent standard curves obtained by both methods has been made. An assay of spe cificity of the antiserum has been made using fluorescence lifetime measure ments because they provide better results. The technique provides good sens itivity, specificity and MDC. (C) 1999 Elsevier Science B.V. All rights res erved.