Laser desorption substrate effects

Information about energy transfer during laser desorption from surfaces is important for the theoretical description of the desorption mechanism and necessary for optimizing applications of laser desorption mass spectrometry. We present a simple method based on laser multiphoton ionization to estimate the internal energy of a laser-desorbed neutral biomolecule, the amino acid tryptophan. The internal energy of neutral laser-desorbed molecules affects ion fragmentation as well as the minimum ionization energy necessary for detecting tryptophan photoions. Data on tryptophan desorbed from glass, graphite, stainless steel, as well as from a silylized glass substrate, were recorded. The silylation of glass reduced the internal energy of desorbed tryptophan dramatically. (C) 1997 American Society for Mass Spectrometry.