Analysis of hydrocarbon polymers by matrix-assisted laser desorption / ionization-fourier transform mass spectrometry

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Abstract

A quick and effective sample preparation is demonstrated for matrix-assisted laser desorption/ionization (MALDI) analysis of nonpolar polymers. Polyisoprene, polystyrene, and polybutadiene polymers were investigated by using as matrix a 2,5-dihydroxybenzoic acid and silver nitrate combination. Silver cationized oligomers produce useful spectra that can be signal averaged to characterize polymer distributions extending up to 6000 u by using a 3-T Fourier transform mass spectrometer. Because an electrostatic ion deceleration protocol was used to extend the mass range, trapping discrimination is shown to exist for molecular weight distributions broader than about 2500 u. However, an integral procedure can be used to reconstruct the true polymer profiles through co-addition of signal transients obtained by using various gated deceleration times. For polymers with narrower mass distributions, silver cationization along with signal averaging provides rapid and accurate polymer characterization for nonpolar polymer systems by using standard MALDI Fourier transform mass spectrometry instrumentation.