LASER-DESORPTION ION-TRAP MASS-SPECTROMETRY OF SELF-ASSEMBLED MONOLAYERS

It is demonstrated that laser desorption ion trap mass spectrometry (L D-ITMS) can be successfully applied to the chemical analysis of a mono layer of adsorbates on a solid surface. Negative ion spectra obtained from LD-ITMS of self-assembled monolayers adsorbed from solutions of a lkanethiols (CH3(CH2)nSH with n = 5, 9, and 15) onto polycrystalline g old surfaces displayed clear ion peaks corresponding to the sulfonate adsorbate species. Sulfonate ions with the general formula CH3(CH2)nSO 3- were detected at m/z 165, 221, and 305, respectively, and were deri ved from the partial oxidation of the corresponding alkanethiol self-a ssembled monolayers. Little fragmentation and no clustering was observ ed in these mass spectra. These results indicate that the sensitivity of LD-ITMS is sufficient to allow its application to a wide array of p roblems in surface science.