Matrix-assisted ultraviolet laser-desorption ionization and electrospray-ionization time-of-flight mass spectrometry of sulfated neocarrabiose oligosaccharides

摘要

Several commercial sulfated neocarrabiose oligosaccharides were analyzed by matrix-assisted ultraviolet laser-desorption ionization time-of-flight mass spectrometry (UV-MALDI-TOF-MS). UV-MALDI-TOF-MS was carried out in the linear and reflecctron modes and, as routine, in both the positive-and negative-ion modes. 2,5-Dihydroxybenzoic acid and nor-harmane were used as matrices. In the positive-and negative-ion modes, with both matrices, peaks corresponding to (M + Na)~+ and (M-Na)~- ions, respectively, were obtained, with only some signals due to glycosidic linkage cleavage (prompt fragmentation). With 2,5-dihydroxybenzoic acid abundant matrix signals were observed; nor-harmane afforded very few matrix signals in both ion modes, but more desulfation (prompt frgmentation) of the compounds occurred. When the desorption/ionization process was highly efficient, the post-source decay (PSD) fragmentation patterns were also investigated; most of the fragments detected derived from glycosidic linkage cleavages. Electrospray-ionization time-of-flight mass spectrometry (ESI-TOF-MS) in the negative-ion mode confirmed, with the observation of the (M-Na)~- and the multiply charged anions, the identify and the purity of the samples.