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.
|Number of pages||6|
|Journal||European Journal of Mass Spectrometry|
|Publication status||Published - 1 Dec 1998|