ORGANIC-SURFACE ANALYSIS BY 2 LASER-ION TRAP MASS-SPECTROMETRY

This paper describes two-laser ion trap mass spectrometry (L2ITMS) for the analysis of organic, polymeric, and biological surfaces. L2ITMS u ses one laser to desorb intact molecules from a surface, a second lase r for photoionization, and an ion trap for single or tandem mass spect rometric analysis. We demonstrate the capabilities of this instrument by performing laser desorption/photoionization/tandem mass spectrometr ic analyses of amino acid and mixed polymer thin films. We then use L2 ITMS in conjunction with X-ray photoelectron spectroscopy to chemicall y analyze the surface of an ion-bombarded polystyrene thin film. Low-e nergy SF5+ ion bombardment causes fluorination of intact polystyrene, partial destruction of the aromaticity of the polystyrene, fluorinatio n of the resultant nonaromatic organic material, and sputtering of the polystyrene. The first of these dominates at 50 eV ion energy, while the latter three dominate at 250 eV.