The effect of counter ions in matrix-assisted laser desorption/ionization of poly(methyl methacrylate)

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Eur. J. Mass Spectrom. 4, 435 - 440 (1998)

The effect of counter ions in matrix-assisted laser desorption/ionization of poly(methyl methacrylate)

Anne-Mette Hoberg, David M. Haddleton and Peter J. Derrick^*
Institute of Mass Spectrometry and Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK. E-mail: .
Anthony T. Jackson and James H. Scrivens
ICI Research and Technology Centre, PO Box 90, Wilton, Middlesbrough, Cleveland, TS90 8JE, UK.

ABSTRACT:

The role of the counter anion in positive-ion matrix-assisted laser desorption/ionization (MALDI) mass spectrometry of poly(methyl methacrylate) (PMMA) has been investigated. When PMMA was analyzed by MALDI in the presence of different alkali metal halides, A⁺X^-, ion yields decreased on changing X^- from I^- to Br^- to Cl^-. The effects of changing the alkali metal cation A⁺ were greater when X^- was chloride than when X^- was iodide. With a mixture of two different alkali metal cations, PMMA showed different affinities for the cations, dependent upon which counter anion was present.

Keywords: MALDI, synthetic polymers, cationization, counter ions

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