Glycosylated proteins,including erythropoietins,monoclonal antibodies,various hormones,constitute major approved therapeutic biological drugs.Sialic acid is important to cell recognition and migration and critical to circulation half life of the protein as exampled by therapeutic protein rhEPO.Thus monitoring protein glycosylation,including sialylation,is important for both glycoprotein characterization and quality control purposes.Standard oligosaccharide profiling (both fluorescently labeled and unlabeled) requires releasing the glycan from the protein and thus is time and labor consuming.Capillary electrophoresis,currently available technique for intact protein sialylation profiling,may not provide enough resolution.Thus an analysis method with both convenience and higher resolution is needed for protein sialylation monitoring.