Minimizing cationization effects in the analysis of complex mixtures of oligosaccharides.

We outline simple methodology for the rapid and selective analysis of 2-aminoacridone (2-AMAC) derivatised oligosaccharides by matrix-assisted laser desorption/ionization mass spectrometry. This involves the addition of small amounts of lithium chloride to the matrix before evaporation of solvent and crystallization. Signals mainly attributed to proton, sodium and potassium adducts are suppressed to a great extent, and a single signal due to (M + Li)+ is observed. This technique is rapid and is most useful for the direct analysis of complex glycan mixtures, after derivatization with 2-aminoacridone and without separation of the individual components.