A noninstrumental immunoassay based on colloidal dyes

Detecting labels based on water dispersions of colloidal textile dyes were developed that are useful in various analytical and diagnostic test systems for a simple visual assessment of the assay. Colored water-insoluble parti cles of dye's were used for the sorptional immobilization of streptavidin o n their surface. The resulting streptavidin-dye (STR-DYE) complexes possess ed a high visualizing capacity and were used for the combined detection of pesticides (simazine and 2,4-dichlorophenoxyacetic acid) by noninstrumental immunoassay (DYE-comb-assay, competitive dot-immunoassay in the comb forma t). The detection limits and the duration of our DYE-comb-assay (4 ng/ml, 2 0-25 min), HRP-comb-assay (competitive dot-immunoassay in the comb format u sing the enzymic conjugate of STR with horseradish peroxidase) (16 ng/ml), and the traditional competitive ELISA (12-16 ng/ml, 1.5 h) were compared. T his DYE-comb-assay is simple enough and can be used under field conditions.