Mass determination of oligosaccharides by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry following HPLC, assisted by on-line desalting and automated sample handling

The off-line coupling of analytical high-performance anion-exchange chromatography (HPAEC) to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is described. The system was applied to the analysis of neutral and acidic xylo-oligosaccharides. For MALDI-TOF MS, on-line desalting of the HPAEC eluent was performed using an anion self regenerating suppressor (ASRS) in series with a cation self-regenerating suppressor (CSRS). The ASRS permitted the exchange of acetate ions with hydroxide ions while the CSRS permitted the exchange of sodium ions with hydronium ions. The continuous desalting of the eluent was achieved by the electrolysis of pure water in both suppressors. Following automated fractionation after HPAEC separation using a 96-well plate fraction collector and computer-controlled MALDI-TOF MS sample preparation using a robot are applied as well. The complete process from HPAEC separation at analytical scale to MALDI-TOF MS could be performed most conveniently, giving molecular mass information overcoming the rather unpredictable HPAEC elution behavior of (unknown) oligosaccharides.