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Quantitative aspects in electrospray ionization ion trap and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry of malto‐oligosaccharides
Author(s) -
Unterieser Inga,
Cuers Julia,
Voiges Kristin,
Enebro Jonas,
Mischnick Petra
Publication year - 2011
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.5105
Subject(s) - chemistry , mass spectrometry , electrospray ionization , ionization , chromatography , analytical chemistry (journal) , matrix assisted laser desorption/ionization , sample preparation in mass spectrometry , ion , ion source , desorption electrospray ionization , desorption , analyte , reagent , extractive electrospray ionization , chemical ionization , adduct , matrix (chemical analysis) , electrospray , organic chemistry , adsorption
Mass spectrometry is widely applied in carbohydrate analysis, but still quantitative evaluation of data is critical due to different ionization efficiencies of the constituents in a mixture. Different size and chemical structure of the analytes cause their uneven distribution in droplets (electrospray ionization, ESI) or matrix spots (matrix‐assisted laser desorption/ionization, MALDI). In addition, instrumental parameters affect final ion yields. In order to study and optimize the latter, an equimolar mixture of malto‐oligosaccharides (DP1‐6) was analyzed using varying target masses for ESI as well as different matrices and laser power for MALDI. The sodium adducts and derivatives for positive ion mode (hydrazones with Girard's T Reagent, GT) and negative ion mode (reductively aminated with o ‐aminobenzoic acid, oABA) were studied. Negatively charged oABA‐labeled malto‐oligosaccharides turned out to be unsuitable for quantification of the malto‐oligomeric composition. Best agreement was achieved when applying target masses in the range of the highest homolog in the mixture in electrospray ionization ion trap (ESI‐IT) (1–2% deviation with GT label or as Na + adducts). Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) gave best results when the laser power was adjusted significantly over the desorption/ionization threshold (1% deviation with GT label). Both parameters show significant influence on the determined oligomeric composition. Consequently, estimation and even quantitative determination of amounts of oligosaccharides in a mixture can be achieved when the analytes are labeled and the proper instrumental parameters are used. Copyright © 2011 John Wiley & Sons, Ltd.