An On-Line Platform for the Analysis of Permethylated Oligosaccharides Using Capillary Liquid Chromatography-Electrospray Ionization-Tandem Mass Spectrometry

Permethylation is one of the most practical modifications for mass spectrometric analysis of carbohydrates. In this study, we showed a facile platform for the on-line permethylation and analysis of acidic N-glycans using capillary liquid chromatography-electrospray ionization-tandem mass spectrometry to elucidate the N-glycan structures derived from glycoprotein samples. Two capillaries, individually packed with NaOH and C₁₈ powder, were coupled to electrospray ion trap mass spectrometer. Prior to mass spectrometry, oligosaccharides were permethylated in NaOH-packed capillary by methyl iodide, and the permethylated glycans were consequently extracted from residual reagents, such as NaOH and methyl iodide, in C₁₈-capillary, instead of using conventional chloroform extraction. After permethylation and purification, the permethylated glycans were released from C₁₈ capillary by acetonitrile, and sprayed into mass spectrometer. Using this on-line strategy, a picomolar range of sialylated N-glycans from bovine fetuin were analyzed by tandem mass spectrometry.