Fig. 2.

Zonal affinity chromatography (ZAC) 1 a compound or mixture is injected onto an affinity column (2). The column (backbone) material that is immobilized with target protein, such as a receptor, retains compounds with affinity. 3 detection of eluted ligands with MS as peaks in the MS trace. 4a–7a snapshots of eluted ligands at different time points during a ZAC analysis. 4b–7b corresponding detection of ligand elution events with MS per ligand. When high-affinity ligands are to be analyzed, continuous infusion of a competitor is necessary to prevent extremely long retention times