PEGylation can bring along many challenges, one of which is the formation of process related impurities. Typically, size exclusion chromatography has been advantageous in removal of these impurities at small-scale, but this is not feasible for large-scale implementation. With the use of High Throughput Screens (HTS), several other purification methods were identified. This poster will highlight a challenging process in which large polymer-protein complexes were conjugated and subsequently purified downstream using HIC chromatography.