Abstract: What is described are methods and apparatus for performing a binding assay for an analyte of interest present in a sample. The methods include the steps of: forming a composition containing the sample, an assay-performance-substance which contains a component linked to a label compound capable of chemiluminescing when triggered, and a plurality of particles capable of specifically binding with the analyte and/or the assay-performance-substance; incubating the composition to form a complex which includes a particle and the labeled component; collecting the complex in a collection zone; introducing into the collection zone a trigger capable of triggering the label such that the label luminesces; and measuring the emitted luminescence to measure the presence of the analyte of interest in the sample.