Abstract: A pre-column derivatization method for the determination of oligosaccharides based on a labeling reagent 3-amino-9-ethylcarbazole (AEC) was proposed. The enamines were generated by the reaction of the reducing ends of oligosaccharides and the primary amines of AEC, and then reduced to secondary amines by NaBH3CN, making oligosaccharides labeled by AEC. The derivatives were separated by reversed-phase high performance liquid chromatography （RP-HPLC）, and then directly analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The HPLC separation was carried out on a Waters Symmetry C18 column (3.9 mm×150 mm, 5 μm) with a gradient elution (acetonitrile and ammonium acetate as mobile phases at a flow rate of 1 mL/min) and ultraviolet detection at 254 nm. Under the optimized derivatization and HPLC conditions, the derivatized oligosaccharides were separated, and the derivatization with AEC increased the sensitivity of MS detection. The developed method for the analysis of oligosaccharides is satisfactory.

Key words: 3-amino-9-ethylcarbazole, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry （MALDI-TOF-MS）, oligosaccharides , high performance liquid chromatography (HPLC)