Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for polymer analysis: solvent effect in sample preparation

Abstract

The success of matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry for the characterization of polymer structures and for the determination of average molecular weights and distributions depends on the use of a proper sample/matrix preparation protocol. This work examines the effect of solvents, particularly solvent mixtures, used to prepare polymer, matrix, and cationization reagent solutions, on MALDI analysis. It is shown that the use of solvent mixtures consisting of polymer solvent does not have a significant effect on the molecular weight determination of polystyrene 7000 and poly(methyl methacrylate) 3750. However, solvent mixtures containing a polymer nonsolvent can affect the signal reproducibility and cause errors in average weight measurement. This solvent effect was further investigated by using confocal laser fluorescence microscopy in conjunction with the use of a fluorescein-labeled polystyrene. It is demonstrated that sample morphology and polymer distribution on the probe can be greatly influenced by the type of solvents used. For sample preparation in MALDI analysis of polymers, it is important to select a solvent system that will allow matrix crystallization to take place prior to polymer precipitation. The use of an excess amount of any polymer nonsolvent should be avoided.

Investigating the effect of mixing ratio on molar mass distributions of synthetic polymers determined by MALDI-TOF mass spectrometry using design of experiments

“…• Different baseline elevations in the low mass tail were described in literature due to different solvent mixtures [9] and due to different matrices as well [30]. The obtained MALDI mass spectra of this study confirm these observations.…”

“…In recent years many factors influencing the quality of MALDI mass spectra of synthetic polymers were investigated especially factors of sample preparation. It has been shown that the matrix type, cationization reagent, their concentrations, as well as the type of solvent or solvent mixture, and the spotting technique affect the polymer distribution [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Besides sample preparation, the instrumentation parameters influence the determined molar mass distribution [17,18].…”

Comparative studies of poly(dimethyl siloxanes) using automated GPC-MALDI-TOF MS and on-line GPC-ESI-TOF MS

“…Mass discrimination occurs with more broadly dispersed polymer samples such that the high molecular weight oligomers within the molecular weight distribution (MWD) are under-represented or not observed at all. Several reports have been written that hypothesize of the root cause for these discrimination effects [21][22][23][24][25][26][27][28].…”

Significant parameters in the optimization of MALDI-TOF-MS for synthetic polymers

“…These parameters, as well as laser energy, were most influential for the polystyrene with dithranol as the matrix. any factors influence the quality of matrixassisted laser desorption/ionization (MALDI) time-of flight (TOF) mass spectra of synthetic polymers [1][2][3][4][5][6][7][8][9][10][11]. Foremost is the nature of the sample itself.…”

“…The detector voltage influences the sensitivity of the detector, but if the detector voltage is too high, a loss in the signal-to-noise may result because of the increase in background noise. To keep the design relatively simple and the amount of data to a minimum, we chose to concentrate on only two sample preparation parameters: matrix type and polymer concentration [6,8,10,21].…”