Identification of heparin oligosaccharides by direct coupling of capillary electrophoresis/ionspray-mass spectrometry.

A direct coupling between capillary electrophoresis (CE) and ionspray (IS) mass spectrometry (MS) has been optimized to identify oligosaccharides obtained by enzymatic digestion of heparin. The separation electrolyte was made compatible with the requirements of a direct coupling using electrolytes made of ammonium acetate buffer, pH 3.5 and 9.2. The different parameters of the CE/IS interface were optimized using a standard mixture of disaccharides: flow rate and composition of the sheath liquid, flow rate of the sheath gas and position of the capillary in the needle. Different combinations of positive or negative CE voltage polarity and positive or negative MS ionization modes were investigated. They allowed for detection orders to be easily reversed and for complementary structural information to be gathered. Finally, the optimized methodology was applied to the separation and characterization of porcine mucosa heparin depolymerized by heparinases II and III.