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

• Published in: Journal of the American Society for Mass Spectrometry 1998-12, Vol.9 (12), p.1303-1310
• Main Authors: Yalcin, Talat, Dai, Yuqin, Li, Liang
• Format: Article
• Language: English
• Subjects: Algorithms; Applied sciences; Cationic polymerization; Crystallization; Desorption; Exact sciences and technology; Fluorescein; Fluoresceins; Fluorescence; Fluorescent Dyes; Indicators and Reagents; Ionization; Ions; Lasers; Mass spectrometry; Microscopy, Confocal; Molecular Weight; Organic polymers; Physicochemistry of polymers; Polymers; Polymers - analysis; Polymethyl methacrylate; Polymethyl Methacrylate - chemistry; Polystyrene resins; Polystyrenes - chemistry; Properties and characterization; Reproducibility; Scientific imaging; Solubility; Solvent effect; Solvents; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Spectroscopy; Structure, morphology and analysis; Weight measurement
• ISSN: 1044-0305; 1879-1123
• DOI: 10.1016/S1044-0305(98)00109-3

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 solvents 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.