Demonstration of an automated Protein A purification and LC-MS mAb subunit analysis of bioreactor samples to screen biosimilar monoclonal antibody (mAb) candidates in comparison to the innovator to support process development. The method was demonstrated to have sufficient sensitivity and precision to quantitively assess N-linked oligosaccharides at levels known to impact pharmacokinetics and effector function activity, in addition to other post-translational modifications (PTMs) such as C-terminal lysine variants and other subunit-specific (LC & Fd’) modifications