Nano-scale liquid chromatography-mass spectrometry of 2-aminobenzamide-labeled oligosaccharides at low femtomole sensitivity

Conventional normal-phase high performance liquid chromatography of fluorescently labeled oligosaccharides with or without on-line mass spectrometry is an established tool for the structure characterization of protein and lipid derived glycans. Here we describe the miniaturization of such a system to the nano-scale using a 75 mum internal diameter normal-phase amide column on-line with electrospray ionization ion-trap mass spectrometry. 2-Aminobenzamide-labeled oligosaccharides have a predictable retention on this normal-phase column that can be expressed as glucose units by comparison to the retention of a standard 2-aminobenzamide glucose polymer mixture. Isobaric compounds are separated on the basis of their structural differences, and by on-line electrospray ionization ion-trap mass spectrometry, the sequence of the monosaccharides can be deduced. The major improvement of the on-line nano-LC-MS system in comparison to conventional systems is the gain in sensitivity with detection of low femtomole amounts of glycans. This implies that LC-MS of 2-aminobenzamide-labeled oligosaccharides can now be performed at higher sensitivity than their analysis with fluorescence detection. (C) 2003 Elsevier B.V. All rights reserved.