Solid state nuclear magnetic resonance as a tool to explore solvent-free MALDI samples |
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Authors: | Hélène Pizzala Caroline Barrère Michaël Mazarin Fabio Ziarelli Laurence Charles |
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Institution: | (1) Chestnut Run Plaza, DuPont Fluorochemicals, Wilmington, DE 19880-0711, USA;(2) Marshall R&D Laboratory, DuPont Performance Coatings, Philadelphia, PA 19146, USA |
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Abstract: | Solid-state Nuclear magnetic resonance (NMR) was used here to explore structural characteristics of samples to be subjected
to matrix-assisted laser desorption/ionization (MALDI) and prepared without the use of any solvent. The analytical systems
scrutinized in NMR were mixtures of a 2,5-dihydroxybenzoic acid (2,5-DHB) matrix and caesium fluoride (CsF), used as the cationization
agent in synthetic polymer MALDI mass analysis, at different molar ratios (1:1, 5:1, and 10:1). Complementary information
could be obtained from 13C, 133Cs, and 19F NMR spectra. Grinding the matrix together with the salt in the solid state was shown to induce a strong modification in
the molecular organization within the MALDI sample. The evidenced mechano-induced reactions allow strong interactions between
the matrix and the cation, up to the formation of a salt, and only occur in the presence of some water molecules. Addition
of a poly(ethylene oxide) polymer as the analyte did not further modify the observed molecular organizations. Although relative
matrix and salt concentrations in the scrutinized samples were unusual for MALDI analysis, mass spectra of good quality could
be obtained and revealed that cation attachment on polymers during the MALDI process is not a matrix-independent event since
a lower ionization efficiency was obtained from highly organized solid samples, mostly consisting of 2,5-DHB caesium salt
species. |
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