Due to the lack of chromophores and poor ionization properties of oligosaccharides, the application of the separation methods with optical or mass spectrometry detection in the characterization of polysaccharides is impeded. Therefore, many derivative strategies with different labels have been applied.
Glycans can be derivatized to introduce a chromophore or fluorophore to facilitate detection after chromatographic or electrophoresis separation. Derivatization can also be applied to the connection of charged or hydrophobic groups at the reducing end to enhance the separation and the detection of glycans. Permethylation as one of derivatization steps is used to stabilize sialic acid residues, improve mass-spectrometric sensitivity, and support detailed structural characterization by mass spectrometry. In addition, many glycan labels also act as a linker for oligosaccharides to attach surface or carrier proteins, allowing for interaction studies with carbohydrate-binding proteins.