Novel conjugates of 5-fluoro-uracil and novel 5-fluoro-uracil immunogens and monoclonal antibodies generated by these immunogens which are useful in immunoassays for the quantification and monitoring of 5-fluoro-uracil in biological fluids.

Extended rhodamine compounds exhibiting favorable fluorescence characteristics having the structure ##STR00001##
are disclosed. In addition, novel intermediates for synthesis of these dyes are disclosed, such intermediates having the structure ##STR00002## In addition, methods of making and using the dyes as fluorescent labels are disclosed.