The CaptureSelect AVB Sepharose HP Leakage ELISA is designed to detect possible leached ligand of adeno-associated viruses (AAV) purified using AVB Sepharose HP affinity resin (Cytiva). Even when covalently attached, small amounts of the AVB Sepharose HP affinity ligand can leach off of the chromatography support and co-elute with the virus particles. This ELISA provides typical sensitivity and accurate quantitation of possible leached ligand greater than or equal to 1 ng/mL. The CaptureSelect AVB Sepharose HP Leakage ELISA can be used as a tool to aid in optimal purification process development and in routine quality control of in-process streams as well as final product.