Characterization of the molecular mass distribution of pullulans by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry using 2,5‐dihydroxybenzoic acid butylamine (DHBB) as liquid matrix

Abstract

The performances of several matrices were investigated for the accurate determination of the molecular mass distributions of pullulans by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The ionic liquid matrix (ILM) 2,5-dihydroxybenzoic acid butylamine (DHBB) gave better and more reliable results than the crystalline matrices 2,5-dihydroxybenzoic acid (DHB) and 2,4,6-trihydroxyacetophenone (THAP). With the ILM it was possible to obtain spectra of pullulans up to more than 100 kDa, the highest molar mass reported thus far. Owing to the known advantages of liquid matrices providing better spot-to-spot reproducibility, an almost noise-free spectrum and constant baselines were obtained when working under optimized conditions. In particular, the extent of in-source fragmentation occurring with this group of fragile polymers was considerably and decisively reduced. Thus, a more reliable representation of the true oligomer and polymer distributions is experimentally attainable, especially for distributions with small polydispersity values. The maximum error in the measured distribution associated with fragmentation was estimated by model calculations describing the changes in the polymer distribution upon different probabilities of fragmentation events. These simulation results indicated that the data obtained by MALDI-TOFMS using the liquid DHBB matrix were of high reliability. In particular, the average value of the distributions, M(w), and the polydispersity were obtained with predicted uncertainties of between 3 and 15% depending on the width of the distribution and the mass of the polymers.

Tandem Mass Spectrometry of Tagged and Permethylated Polysaccharides

“…Due to their ability to dissolve a wide range of analytes they have been used in a number of analytical techniques (Schnöll-Bitai, et al, 2008). In 2001, ionic liquids were introduced as matrices in MALDI MS for the analysis of biomolecules and synthetic polymers (Tholey & Heinzle, 2006).…”

“…the determination of the molecular mass distribution of polysaccharides (pullulans) which are used as calibration standards in aqueous size-exclusion chromatography (Schnöll-Bitai et al, 2008). In most cases the ionization process in ILMs led to protonated species of the analytes, very similar to solid matrices.…”

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

“…This indicates that with high laser power less selectivity in ionization, and, consequently, less discrimination of higher homologs with HABA, occurs. Likewise, for the molecular mass distribution of synthetic polymers best results were achieved at high laser power since here less discrimination of high mass compounds occurs, unfortunately with the risk of in‐source fragmentation of lower homologs of the polymer . No fragmentation was detected in our experiments.…”

“…Likewise, for the molecular mass distribution of synthetic polymers best results were achieved at high laser power since here less discrimination of high mass compounds occurs, unfortunately with the risk of in-source fragmentation of lower homologs of the polymer. [35,36] No fragmentation was detected in our experiments.…”

“…Compared to ESI MS, MALDI-TOF MS is more often applied for determination of molecular weight distribution, [30][31][32][33][34] although a critical investigation of parameters is also necessary for this method. [35][36][37] Momcilovic et al analyzed an equimolar mixture of malto-oligosaccharides (DP1-7) by MALDI-TOF (matrix DHB, no declaration of laser power) on the one hand without labeling and on the other hand after reductive amination with dimethylamine. Without derivatization a strong discrimination of lower mass components was observed, while after labeling the higher homologs were underrepresented.…”