| abstract |
Improved methods for determining very low concentrations of substances present in fluid samples are provided by employing light emitting tracer compounds and (1) counting the photons emitted therefrom while discriminating against noise, nonspecific light, and quenching effects of the sample, or (2) counting the photons emitted therefrom over a predetermined integrated light flux, or a combination of (1) and (2). Further, novel fluorescently labeled low molecular weight antigens are provided which can be employed in competitive binding techniques in which the above described photon counting methods are useful. A homogeneous competitive binding assay, employing photon emitting tracer materials, which eliminates the need for separating bound from unbound materials is also provided. Finally, a modified enzyme amplification technique is set forth employing enzymes active in the bound phase to provide assay techniques useful for extremely low concentration assays. |