Discrimination of sulfated isomers of chondroitin sulfate disaccharides by HILIC-MS

Chondroitin sulfate (CS) glycosaminoglycans are biologically active sulfated polysaccharides that pose an analytical challenge for their structural analysis and functional evaluation. In this study, we developed a hydrophilic interaction liquid chromatography separation method and its on-line coupling to mass spectrometry (MS) allowing efficient differentiation and sensitive detection of mono-, di-, and trisulfated CS disaccharides and their positional isomers, without requiring prior derivatization. The composition of the mobile phase in terms of pH and concentration showed great influence on the chromatographic separation and was varied to allow the distinction of each CS without signal overlap for a total analysis time of 25 min. This methodology was applied to determine the disaccharide composition of biological reaction media resulting from various enzymatic transformations of CS, such as enzymatic desulfation of CS disaccharides by a CS 4- O -endosulfatase, and depolymerization of the CS endocan by chondroitinase lyase ABC. Graphical abstract