Here we employ a nLC-MS/MS method to separate small amounts of purified immunoglobulins to characterize the N-glycan reportoire and site occupancy of bulk serum antibodies. Using this method, we have established, for the first time within individual donors, the N-linked glycan repotoire for bulk IgG1, IgG4, IgA1, IgA2 and IgM in healthy individuals. This is crucial for developing a platform to define disease-specific N-glycan signatures for different isotypes to help tune antibodes to induce protection.