Chromium solutions have been used as wet chemical modifiers for polymer microtitre plates used in improving immunoassay performance. However, polypropylene has been excluded from the list of potentially modifiable substrates (AnteoTechnologies, 2015). Here we show that untreated polypropylene microtitre plates can indeed be modified using a [Cr(OH)6]3- complex. Compared to unmodified polypropylene, the chromium modified surfaces demonstrate an up to 4-fold improvement in both assay sensitivity and signal intensity in an antigen capture ELISA. Atomic force microscope (AFM) images indicate that the chromium complex facilitates dispersion of the antibody, reducing aggregation.