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Matrix Clusters and Polymer-Matrix Adducts in the MALDI Analysis of Polystyrene

Published

Author(s)

R J. Goldschmidt, Charles M. Guttman

Abstract

The formation of matrix cluster ions and of polymer-matrix adduct ions in the matrix-assisted laser desorption/ionization (MALDI) analysis of polystyrene was investigated using layered sample preparations. It has been shown by post-source decay (PSD) experiments that decay of polymer-matrix adducts plays a role in the production of cationized polystyrene ions in MALDI. Matrix clusters compete for cations with polystyrene and may also play a role in the mechanism of cation attachment to polystyrene. Two methods were used to prepare layered samples. In the first method, an aqueous silver or copper salt solution was deposited on top of a dried polystyrene-matrix layer. Since neither polymer nor matrix are soluble in water, there is no opportunity for solution phase chemistry to occur between the metal and the polymer or matrix. In the second method, electrospray sample deposition was used to deposit separate layers. Scanning electron microscopy (SEM) indicates that electrosprayed droplets arrive at the MALDI target dry, and so again there is no opportunity for solution phase chemistry to occur between species in the separate layers. Experiments in which a salt layer was deposited on top of a polymer-matrix layer indicated that matrix salt formation and cation attachment to polystyrene and to matrix species readily occur without solution phase interactions. Experiments in which a second matrix layer was deposited on top of a polymer-matrix-salt layer indicated that matrix clusters and polymer-matrix adducts are also readily formed without solution phase interactions, though some direct desorption of such species is not ruled out. Interactions occurring during expansion of material from the sample subsequent to the laser pulse are clearly important in the formation of species observed in MALDI mass spectra.
Citation
ASMS Conference on Mass Spectrometry and Allied Topics
Volume
41(1)

Keywords

adduct formation, cluster formation, ionization mechanism, MALDI, polystyrene, post-source decay

Citation

Goldschmidt, R. and Guttman, C. (2000), Matrix Clusters and Polymer-Matrix Adducts in the MALDI Analysis of Polystyrene, ASMS Conference on Mass Spectrometry and Allied Topics, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851745 (Accessed April 22, 2024)
Created January 1, 2000, Updated February 17, 2017