Abstract: A homogeneous assay for determining the aflatoxin content in agricultural products uses the technique of fluorescence polarization. A solvent is used to extract aflatoxins from a sample of the agricultural product. A mixture is prepared by combining the extract with a tracer and with a monoclonal antibody specific for aflatoxin. The tracer is able to bind to the monoclonal antibody to produce a detectable change in fluorescence polarization. The tracer is prepared by conjugating an aflatoxin oxime to a suitable fluorophore. The fluorescence polarization of the mixture is measured. The aflatoxin concentration of the mixture may be calculated using a standard curve obtained by measuring the fluorescence polarization of a series of aflatoxin solutions of known concentration.

Abstract: An optical filter (100) comprises a multimode waveguide (126) and first (122) and second (124) coupling waveguides which communicate with lateral sides of the multimode waveguide. The filter operates by reproducing an optical field distribution input to the multimode waveguide via one of the coupling waveguides at the position in the multimode waveguide where the other coupling waveguide communicates with the multimode waveguide. This occurs for radiation of a wavelength to be filtered but not for radiation of other wavelengths.