Quantitative aspects in electrospray ionization ion trap and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry of malto‐oligosaccharides

Abstract

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.

Analysis of carbohydrates and glycoconjugates by matrix‐assisted laser desorption/ionization mass spectrometry: An update for 2011–2012

“…Instrumental parameters also affect final ion yields. To optimize the latter parameter, Unterieser et al () have studied various parameters relevant to quantitation by both ESI and MALDI. For MALDI‐TOF analysis, an equimolar mixture of malto‐oligosaccharides (DP1‐6), both native and derivatized with Girard's T (GT, 1/55 ) reagent (positive ion) or 2‐AA (negative ion), was analyzed using different matrices (2‐(4′‐hydroxyphenyl)azobenzoic acid [HABA, 1/32 ], THAP, indoleacrylic acid [IAA, 3/5 ]) and super‐DHB (sDHB), and laser power.…”

Mass Spectrometric Investigation of the Chemical Composition of Caramel Formed upon Heating of Disaccharides

“…That classification exists without any further structure suggestions due to the complexity of created products during caramelization. Mass spectrometry (MS) has been applied for structural investigation of saccharides, using mainly electrospray ionization (ESI) [14][15][16] and matrix-assisted laser desorption/ionization (MALDI) [17][18][19]. Tandem mass spectrometry (MS/MS) is demonstrated to be a valuable tool in the structural D DAVID PUBLISHING characterization of carbohydrates to achieve thorough information regarding their structure [20,21].…”

Relative ion intensities of maltooligosaccharide ethers in electrospray ionization ion trap mass spectrometry: A quantitative evaluation

“…With increasing DP these profiles become narrower, and thus the analytes being compared become more similar in mass and polarity. Thus, the drop of relative sensitivity coefficients (k Me-d3 /k Me ) with increasing DP is probably of low relevance for randomly substituted polymer derivatives [10], but have to be considered in case of block like structures [30]. Moreover, it is of interest to understand the reason behind this behavior.…”

“…The introduction of a charged tag, amino benzoic acid for negative ion mode, and Girard's T for positive ion mode [31], can level off differences in sodium complexation ability and at the same time influence surface activity. [30]. Therefore, we tested whether labeling can level off the decrease in relative sensitivity observed with the normal ESI-MS for oligomers of higher DP.…”