The present invention concerns novel synthetic blocking reagents for the reduction of non-specific bindings in solid phase assays that rely on biological and specific recognition, e.g., in enzyme-linked immunosorbent assays (ELISAs). The invention provides the use of compounds as blocking reagents as well as kits comprising these compounds. The compounds comprise one or more poly(ethylene glycol) moieties, one or more alkyl- or aminoalkyl groups and another unit bridging the aforementioned groups, wherein the compound comprises at least one amino group.