Abstract: A method of determining the quantity of two or more species in a polydisperse sample is provided. The method comprising the steps of: performing a series of dilution steps of the polydisperse sample; adding a probe into the polydisperse sample, wherein the probe is configured to bind to two or more species to form two or more probe-target species complexes; separating two or more probe-target species complexes at each dilution step into two or more bins; determining the concentration of each separated probe-target species complex in each bin at each dilution step; and determining the quantity of each target species in the sample and/or the affinity of each target species to the probe.